Question

a b c
10x - 18
#11: x = ____ *
7
#12: ab = ____ *
39
#13: bc = ____ *
13
#14: ac = ____ *
your answer

Explanation:

Step1: Assume AB + BC = AC

Let AB = 39, BC = 13, AC = 10x - 18. Then 39+13 = 10x - 18.

Step2: Simplify left - hand side

39 + 13=52, so 52 = 10x - 18.

Step3: Solve for x

Add 18 to both sides: 52 + 18=10x, 70 = 10x. Then x = 7.

Step4: Find AC

AC = 10x - 18, substitute x = 7, AC = 10×7 - 18 = 52.

Answer:

#11: 7
#12: 39
#13: 13
#14: 52