Answer:
10
Step-by-step explanation:
Pythagorean Theorem:
[tex]a^{2} + b^{2} = c^{2}[/tex]
Putting the values in the variables:
[tex](10 + x)^{2} + 15^{2} = 25^{2}[/tex]
[tex](10 + x)^{2} + 225 = 625[/tex]
[tex](10 + x)^{2} = 400[/tex]
[tex]10 + x = \sqrt{400}[/tex]
[tex]10 + x = 20[/tex]
[tex]x = 20 - 10 = 10[/tex]
