Answer
$c=-1$
Work Step by Step
The variable appears only in the denominators, so we know we should use the Cross Products Property. Recall, cross multiplying refers to when we multiply the numerator of the first fraction by the denominator of the second fraction and set that equal to the numerator of the second fraction times the denominator of the first fraction. We first cross multiply to get that $35c+20=6c-9$. We first subtract by 6c on both sides to get that $29c+20=-9$. Next, we cancel out addition by subtracting by 20 on both sides to get that $29c=-29$. Finally, we divide by 29 on both sides to get that $c=-1$.
