Answer:
BC = 21
Explanation:
We know that AB + BC = AC
First we need to solve for x so using what we know lets set up the equation.
AB = 7x + 8
BC = 3x + 6
AC = 64
So (7x + 8) + (3x + 6) = 64
Combine like terms and solve.
10x + 14 = 64
10x = 50
x = 5
Now that we know that x = 5, to find the number for BC let's put that into the BC expression
3(5) + 6 = 21
There's your answer. BC = 21
Now if you really wanna make sure you can input the values we've found into the equation we first made.
AB + 21 = 64
7x + 8 + 21 = 64
7(5) + 8 +21 = 64
35 + 29 = 64
64 = 64