Answer:
21
Step-by-step explanation:
You can do it two different ways.
1st. Find the scale factor by dividing - 75/25=3 or 72/24=3
This means the scale factor is three
Then multiply the remaining side (7) by the scale factor (3) to get: 21
2nd. Use the Pythagorean Theorem - 75²-72²=x²
441 = x²
√441=x
x=21