Respuesta :

3m+21=6m
=>21=6m-3m
=>21=3m
=>7=m
Therefore option A is the answer

Here triangles LRU and LAU are congruent

So side RU=AU

3m+21=6m

subtracting 3m from both sides

21=6m-3m

3m=21

dividing both sides by 3

m=21/3 = 7

Answer is A. m=7