Answer:
x = 5
Explanation:
The sides are in proportion.
The proportion is 20/36
The other sides must be in the same proportion: 5x / 45
5x/45 = 20/36 You can reduce the left side by dividing top and bottom by 5
1x / 9 = 20/36 You can reduce the right side by dividing by 4
x / 9 = 5/9 at this point you should be able to see that x = 5, because the denominators are the same.
That is the answer.
However you can extend this by cross multiplying
9x = 45 Divide by 9
x = 45/9
x = 5