If cosine of x degrees equals three-fifths, what is the value of b?

triangle LMN in which angle M measures 90 degrees, angle L measures x degrees, LN measures 20 units, and LM measures 3b units

b = 4
b = 5
b = 6
b = 7

If cosine of x degrees equals threefifths what is the value of b triangle LMN in which angle M measures 90 degrees angle L measures x degrees LN measures 20 uni class=