algebra
posted by Rick .
One day a store sold 45 pens, the zippedy do's at $8.50 & The Royal Blues at $9.75. In all, $398.75 was spent on the pens. How many Royal Blues were sold that day?

45=Z+R
9.75R+8.5Z=398.75
R=45Z
put that in for R in the second equation, and solve.