if you x A by 7 and B by 3 the sum has a diff. of 12, 3/4 of A and 2/3 of B=21 solve for A&B
1) 7A + 3B = 12 Multiply by 8
1a) 56A + 24B = 96
2) 3/4A + 2/3B = 21 Multiply by 12
2a) 9A + 8B = 252 Multiply by 3
2b) 27A + 24B = 756 Subtract 1a) from 2b)
1a) 56A + 24B = 96
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-29A = 660
A = 660/-29 = -22.76
1) 7A + 3B = 12 plug in A = -22.76
7(-22.76) + 3B = 12
-159.32 + 3B = 12
3B = 171.32
B = 57.11
A= -22.76, B = 57.11