Question 1189317
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When Mia buys 4 pens and 1 pencil, she has $5 left; the number of dollars she starts with is 4a+b+5.<br>
When she buys 2 pens and 2 pencils, she has $3 left; the number of dollars she starts with is 2a+2b+3.<br>
Since those two expressions represent the same number, set them equal to each other and simplify to get an equation in a and b.<br>
4a+b+5=2a+2b+3
2a-b=-2 [1]<br>
If Edward arrives with the same number of dollars that Mia started with, they can buy 7 pens and 4 pencils with all their money.<br>
The total amount of money the two of them have is twice what Mia started with; and with that amount of money they can buy 7 pens and 4 pencils with no money left.  Write an equation that says that and simplify to get a second equation in a and b.<br>
8a+2b+10=7a+4b
a-2b=-10 [2]<br>
Solve the pair of equations [1] and [2] by your favorite method.<br>
I'll let you choose the method to use and work the problem to find the answer.<br>
(Note: you should end up with the probably unreasonable answer that each pen costs $2 and each pencil costs $6....)<br>