Given.
[tex](3c-8d=7)=(c+2d=-7)[/tex]
Multiply 4 to the second equation.
[tex]4(c+2d=-7)[/tex]
[tex]3c+8d=-28[/tex]
Compare the like terms.
[tex]4c+3c-8d+8d=7-28[/tex]
Solve.
[tex]7c=-21[/tex]
Divide 7 to both sides
[tex]\frac{7c}{7}=\frac{-21}{7}[/tex]
[tex]c=-3[/tex]
Substitute (-3) for c into the original second equation.
[tex]c+2d=-7[/tex]
[tex]-3+2d=-7[/tex]
Add (3) to both sides.
[tex](-3+2d=-7)+3[/tex]
[tex]2d=-4[/tex]
Divide (2) to both sides.
[tex]\frac{2d}{2}=\frac{-4}{2}[/tex]
[tex]d=-2[/tex]
Check your work.
[tex]3(-3)-8(-2)=7[/tex]
[tex]-9+16=7[/tex]
[tex]7=7[/tex]
[tex]c+2d=-7[/tex]
[tex]-3+2(-2)=-7[/tex]
[tex]-3-4=-7[/tex]
[tex]-7=-7[/tex]
Therefore your answer is.
[tex]c=-3\\d=-2[/tex]
