Carol bought two chairs with triangular backs. For what value of x can you use a triangle congruence theorem to show that the triangles are congruent?
Which triangle congruence theorem can you use? Explain.

x = 4

Step-by-step explanation:

Two sides, GH and GI, in ∆GHI are of the same side length as corresponding two sides, TU and TV, in ∆TUV.

To prove that both triangles are congruent using the SSS Congruence Theorem, therefore, the their third sides, HI and UV must be equal.

Therefore,

9x - 21 = 15

Add 21 to both sides

9x - 21 + 21 = 15 + 21

9x = 36

Divide both sides by 9

x = 4