Question

-5(c+15)<75

Answer 1

Expand and transpose:

-5(c+15)<75
-5c - 75 < 75
add 5c to both sides:
-5c+5c -75 < 75 + 5c
-75 < 75 + 5c
subtract 75 from both sides
-75-75 < 75-75 + 5c
-150 < 5c
Switch sides:
5c > -150
Divide by 5 on both sides:
5c/5 > -150/5
c > -30