Question

What is the algebraic expression that describes the monthly pay? Let x be the hours of training.

Answer 1

See which equation the values fit.

eg A 
10 hours:  so  monthly pay is   10*10 + 120   = 1300
0
Looks good so far  try  the other values 

Answer 2

For every 10 hours of training, monthly pay increases by 100
that means that for every 1 hour, monthly pay increases by 10
so the answer must be in the form 10x + something
let's take the 1st row in the table:
10 hours of training = 1300 monthly pay
10x+ something = 1300
10*10 + something=1300
something = 1200
therefore, monthly pay = A. 10x+1200