Answer :
Easily move nx to left and a to the right side
mx-nx=-2-a
take x common factor
x(m-n)=-2-a
divide by (m-n)
x=(-2-a)/(m-n)
that said
mx-nx=-2-a
take x common factor
x(m-n)=-2-a
divide by (m-n)
x=(-2-a)/(m-n)
that said