Ellen,

Suppose that each pen costs $P and each stapler costs $S. The statement that "six pens and four staplers cost $7.10" means that the sum of the costs of six pens and four staplers is $7.10. Written as an equation this becomes

6 × P + 4 × S = 7.10.

Write a similar equation that results from the statement that "four pens and seven staplers cost $9.50". You will then have two equations in the unknowns P and S. Look at my response to Leslie to see a method for solving these equations for S and P.

Penny