Solve for y
y=28
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y\times 15=21\times 20
Variable y cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by 21y, the least common multiple of 21,y.
y\times 15=420
Multiply 21 and 20 to get 420.
y=\frac{420}{15}
Divide both sides by 15.
y=28
Divide 420 by 15 to get 28.
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