Yes
Five
A ten foot spread axle trailer is allowed 20,000 lbs. per axle, for a total of 40,000 lbs.
An 18 wheeler consists of a tractor (meaning something that pulls) and a trailer (meaning something that follows.) A semi tractor-trailer rig has a trailer that sits on top of the frame of the tractor on a coupling device called a "fifth wheel." The tractor has ten wheels with two on the front axle and four on each drive axle in the rear. The trailer has two axles with 4 wheels each. The tractor and trailer together are informally called a rig. Is that what you were after?
A tandem truck usually refers to the amount of axles on the trailer or tractor. A single drive axle on a tractor would be referred to as a single, or the same for one axle on the trailer. I have seen it referred to the amount of tires on the end of an axle. When there are two tires on the end of the axle, that would be referred to as a dual, not a tandem.
What type of truck and trailer? For all I know, you could be talking about a Ford F650 and a single axle utility trailer. If you're referring to Class 8 vehicles, something like a single axle tractor towing a single axle trailer would be allowed an interstate GVW of 52,000 lbs.
$70 for a 5 axle tractor trailer
"18 wheeler" referred to tractor-trailer units with a total of five axles (four wheels per drive and trailer axle plus two wheels on the steer axle = 18 wheels). However, it has become a common expression for tractor-trailer units in general, whether or not they have 18 wheels.
"Inner-Bridge" refers to the following: For the Interstate Highway System, inner-bridge legal weight limits are established. There is a weight limit for the truck tractor portion of the truck tractor/semi-trailer combination and a weight limit for the latter part of the combination. The extreme axle distances for each of the two portions are both designated as inner-bridge limits. The inner-bridge for the truck tractor portion is the distance from the center of the steering axle to the center of the last truck tractor axle. The inner-bridge for the latter portion is the distance from the center of the rear axle of the tractor or the center of the first axle of the rear axle group of the tractor to the center of the last axle of the trailer.
They vary, but I think the avg woube about 19,000lbs.
Mini trucking? That's a new one on me. You might be thinking of what's referred to as "hotshot" trucking, which is a single axle trucking pulling a multi-axle trailer. This can be anything from a one ton pickup pulling a gooseneck trailer up to a single axle tractor-trailer power unit pulling a semi trailer.
It depends on the commercial vehicle, how it's licensed, the state it's running in, and a lot of other things, but a tractor-trailer combination with tandem axles on the tractor and the trailer can generally carry 80,000 pounds--12,000 on the front axle and 34,000 on the tractor and trailer tandems.
25,000 - 40,000 lbs. or more, depending on specifics. When you say "tractor-trailer", you're citing an all-inclusive category which would include everything from a single axle tractor pulling a 28' single axle trailer up to heavy haul units of over 20 axles... I've personally run combinations which have weighed in excess of 250,000 lbs. empty.