Question 253809

c-5d=2     
2c+d=4
double the first
2c-10d=4
2c+d=4
As you can see we have 2c in the first and 2c in the second
and after subtracting 10d we get 4
but we also get 4 after adding d
which means that d must equal -10d
d=-10d
which would lead to d being 0 or 1=-10

so d=0
therefore c=2