$\"\"$

The equations are $\"\"$ .

$\"\"$ Equation (1)

$\"\"$ Equation (2)

Since $\"\"$ , substitute $\"\"$ for c in the first equation.

$\"\"$

$\"\"$ $\"\"$

$\"\"$ (Add 4 to each side) \ \

$\"\"$

$\"\"$ (Subtract 3d from each side)

$\"\"$

Substitute $\"\"$ in second equation.

$\"\"$

c = 6 \ \ $\"\"$

The solution is $\"\"$ .