How to do substitution in algebra like 5c-d-11=0,4d+3c=-5

Question

anonymous · Answer

Can any one help ? I have a exam tomorrow

shinalcantara · Answer

since it's given that you have 2 variables which doesn't have values, then substitution is a good idea of solving for the values.
5c-d-11 = 0  -------eqn 1
4d + 3c =-5  -------eqn 2
first, try to examine which of the two is simple such that when you'll find it's value in terms of the other variable you'll have a simple equation.
Let's choose eqn 1 since d has 1 as a coefficient
5c-d-11=0
now transpose d to the other side making it
5c-11=d   or
d = 5c-11   -----eqn 3

now you are ready to substitute eqn 3 to eqn 2
4d + 3c = -5
since you have the value for d from eqn 3, you'll have
4(5c-11) + 3c = -5
now simplify that equation and you'll get the value for c

shinalcantara · Answer

once you'll have the value for c, you can find d by substituting c's value to eqn 3

anonymous · Answer

Thanks :)

shinalcantara · Answer

yw :)