Answer:
3m = 18
Step-by-step explanation:
9 + 12m = 6 + 15(m - 1)
9 + 12m = 6 + 15m - 15
3m = 18
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Because base angles are congruent, both angle A and B are congruent. If the two triangles are congruent, then the base angles are the same, meaning 5x=50*. Divide by 10 and you get the answer of x=5. :) Hope this helps!