The number of students working less than 20 hours is

You would use PEMDAS so that means you would start by multiplying 3 with the parentheses 3(2+6d) on both sides then you would combine like terms so you would add 18d+18d. Then you would subtract 6- -5 on both sides then solve for a one-step equation

3(2+6d)-5=3(2+6d)-5
6+18d-5=6+18d-5
6+36d-5=6-5
1+36d=1
-1. -1
36d/36. 0/30
D=0