Question 1183956
If 4M+N=20 and N+P=20, what is the value of M?
try this
4M + N + __ = 20
__ + N +  P = 20
---------------------subtraction eliminates N
4M - P = 0
P = 4M
:
Replace P with 4M in the second equation
N + 4M = 20
which is essentially the same as the 1st equation, so unable to go further