Thirty coins,all dimes and nickels,are worth $2.60. How many nickels are there?
1 answer:
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9514 1404 393
Answer:
(x, y) = (-1, -3)
Step-by-step explanation:
The equations are "consistent" and "not dependent." This will be the case whenever the ratios of x- and y-coefficients are different.
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We can solve this by "elimination" by multiplying the first equation by -4 and adding the result of the second equation being multiplied by 7.
-4(2x -7y) +7(7x -4y) = -4(19) +7(5)
-8x +28y +49x -28y = -76 +35 . . . . eliminate parentheses
41x = -41 . . . . . simplify
x = -1 . . . . . . . divide by 41
Using the second equation, we find y to be ...
(7x -5)/4 = y = (7(-1) -5)/4 = -12/4 = -3
So, the solution is (x, y) = (-1, -3).
