Method of substitution

Solve the following simultaneous equations.
1.2c+5d=27..........(1)
c+2d=9.............(2)


2.m-n=2.......(1)
m+3n=14......(2)


(1)From 2, c+9-2d....3
sub 3 into 1

2(9-2d)+5d=27
d=9
sub d=9 into 3
c=9-2(9)
c=-9


(2)from 1,m=2+n.....3
sub 3 into 2,2+n+3n=14
n=3
sub n=3 into 3
m=5