Create a proportion for x first. Use known values.
[tex] \frac{4}{x} =\frac{12}{21} [/tex]
84 = 12x
Divide both sides by 12.
x = 7
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Create a proportion for y.
[tex] \frac{12}{y} =\frac{4}{10} [/tex]
120 = 4y
Divide both sides by 4.
y = 30
[tex] \boxed {x = 7,~y = 30} [/tex]
