A chemistry stockroom has two alcohol solutions, a \( 30 \% \) and a \( 75 \% \) solution. How many deciliters of each must be mixed to obtain \( 90 \) deciliters of a \( 65 \% \) solution?
let the quantity of 30% of alcohol be x
and let the quantity of 75% of alcohol be y
0.3x+0.75y=90(0.65) = 58.5