First I would isolate "x"
5x + 7 ≤ 32 Subtract 7 on both sides
5x + 7 - 7 ≤ 32 - 7
5x ≤ 25 Divide 5 on both sides to get "x" by itself
x ≤ 5 [x is less than or equal to 5]
When the sign is ≤ or ≥ ("less/greater than or equal to"), the dot is filled in.
When the sign is < or >, the dot is not filled in/open circle.
Your answer is C