Answer:
x=9
Explanation:
For this question, you would have to use the Pythagorean theorem.
Pythagorean theorem formula: a^2+b^2=c^2
In a triangle, The base of the triangle is A, the height is B, and the hypotenuse is C. In this question, A is 12, B is x, and C is 15. We can use the formula to solve this problem
12^2+x^2=15^2
144+x^2=225
144-144+x^2=225-144
x^2=81
x=√81
x=9
Hope this helps! I will also upload a photo because the ^2 stuff might look confusing (sorry for the bad quality)!
