Answer:
The answer to your question is 10.5 in
Step-by-step explanation:
Data
First triangle
height = x
base = 7 in
Second triangle
height = 12 in
base = 8 in
Process
1.- Use proportions to solve this problem, relates the sides of a triangle with the same sides of the other triangle.

2.- Multiply both sides by 7

3.- Simplify
x = 
4.- Result
x = 10.5 in
The answer to the question
Answer: x=95 and y=17
Step-by-step explanation:
X-y=78
6y=7+x
6y-7=x
6y-7-y=78
5y-7=78
5y=85
y=17
x-17=78
x=78+17
x=95