Solve for y
y=21
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0.2y=4.2
Combine 0.9y and -0.7y to get 0.2y.
y=\frac{4.2}{0.2}
Divide both sides by 0.2.
y=\frac{42}{2}
Expand \frac{4.2}{0.2} by multiplying both numerator and the denominator by 10.
y=21
Divide 42 by 2 to get 21.
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