Uh ok. what does of mean in mathematics?

Evaluate the expression for the given value of the variable 7a - 4a for a =8

Tim earns $120 plus $30 for each lawn he mows.write an iniqualityvto represent how many lawns he needs to mow to make more than $310

Order the equations from least to greatest based on the number of solutions to each equation.-4^x -1 = 3^(-x) – 2 -3x + 6 = 2^x+13^x – 3 = 2x - 2