# math

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DQ sells 6 times as many orders of french fries as sonic everyday. If both sold 60 more orders DQ would only sell 3 times as many fries. How many do each sell before and after the incease?

math - DrBob222, Wednesday, December 23, 2009 at 4:34pm
S = number FF Sonic sells.
D = number FF DQ sells.
===========================
D = 6S every day.
If each sells 60 more, then
D + 60 = 3(S + 60) or
D + 60 = 3S + 120 or
D = 3S + 120
=========================
The two equators are as follows:
D = 6S
D = 3S + 120
Solve these two simultaneous equation for D and S (before the addition of 60), then add 60 to each to determine the number sold after adding 60 to each. Post your work if you get stuck.

math - petie, Thursday, December 24, 2009 at 9:14am
Where did the 120 come from?

• math -

The 120 came from a multiplication error.

3(S + 60) = 3S +180

I hope this helps.

• math -

PsyDAG is correct. I made two errors but they corrected each other; the final two final equations to solve simultaneously are correct.

If each sells 60 more, then
D + 60 = 3(S + 60) or
D + 60 = 3S + 120 or This should be
D + 60 = 3S + 180 which leads to
D = 3S + 120 and that is the same as the original. I was thinking faster than I was writing.

D = 3S + 120