Answer:
x = 18
Explanation:
We can use a proportion to solve for x.
30/x = 40/24
Cross-multiply
40x = 720
Divide by 40
x = 18
Check the answer
30/18 = 40/24
30 x 24 = 18 x 40
720 = 720
This means that we can be sure our answer is correct. If the answer didn't produce a true statement when substituted into the original proportion, we would know our answer was incorrect.