Me on problem 1 of linear expression

I think the answer is A.
As there is brackets we need to work this out first. Let's give x a value of 1 to make it simpler.
3x1+3/4=15/4
5/4x3= 15/4.
I do apologise if I have got this wrong, this was the best I could do.
(Fun trick for remembering what comes first: BIDMAS
Brackets
Indices
Division
Multiplication
Addition 
Subtraction
Hope I helped)

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.