Answer:
According to the problem, think of a triangle with:
leg 1
= 28
leg 2
= 21
Hypotenuse
= 5x
-So, to find the missing hypotenuse, you need to use the "Pythagorean Theorem" in order to solve and get the hypotenuse:
![a^2+b^2=c^2](https://img.qammunity.org/2021/formulas/mathematics/middle-school/96dopf217hvzc3zhswffnjr8l5f26vmjhb.png)
![28^2 + 21^2 = (5x)^2](https://img.qammunity.org/2021/formulas/mathematics/high-school/frrw0psis9ody7zwm5g22631zuk2nxliuw.png)
Then, start solving:
![28^2 + 21^2 = (5x)^2](https://img.qammunity.org/2021/formulas/mathematics/high-school/frrw0psis9ody7zwm5g22631zuk2nxliuw.png)
![781 + 441 = 25x ^2](https://img.qammunity.org/2021/formulas/mathematics/high-school/jkyr6lt28zieza350y3cocr84141vjociw.png)
![1225 = 25x^2](https://img.qammunity.org/2021/formulas/mathematics/high-school/c9hp61wquse5rtutiyvu3ty3r5r7ug74qe.png)
![25x^2 = 1225](https://img.qammunity.org/2021/formulas/mathematics/high-school/t5jy4hmhg16g18e0h2afuxswo3lvqlph67.png)
![(25x^2)/(25) =(1225)/(25)](https://img.qammunity.org/2021/formulas/mathematics/high-school/i3nurcfratmndpi6f0yzx7om986jenwh16.png)
![x^2 = 49](https://img.qammunity.org/2021/formulas/mathematics/high-school/kg9nk14u79mlenq0plw8n6t83fiu1v8q7x.png)
![√(x^2) = √(49)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/zp863dxn3atep7nawl69hzcjqnx7zn5sfe.png)
-Since, the hypotenuse has length of 5x meters, this could mean:
![5x = 5* 7= 35](https://img.qammunity.org/2021/formulas/mathematics/high-school/1bj4fazatsrpsps00ypgj54f0kh7ri2o75.png)
So, the answer is
![x = 7](https://img.qammunity.org/2021/formulas/mathematics/middle-school/haui06dyzu06cccqprdnwfvnybjm6zc7di.png)