A+B=15 —>A+15=B(plug this into the other equation)
60a+30b=600
60a+30(a+15)=600
60a+30a+150=600
90a+150=600
90a=450
A=5 (plug back in to first equation)
A+B=15
5+B=15
B=10
They have 5 of the Model A and 10 of model B.
Let the DVD = x
let the CD = y
x+y = cost
Answer:
Rational number as denominator is not equal to zero and numerator is a integer.