How do you solve #\frac{3}{10}=\frac{9}{y}#?

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Answer 1 · 2017-07-30T22:46:03

See a solution process below:

First, we can "flip" each fraction:

#3/10 = 9/y# becomes:

#10/3 = y/9#

Now, multiply each side of the equation by #color(red)(9)# to solve for #y# while keeping the equation balanced:

#color(red)(9) xx 10/3 = color(red)(9) xx y/9#

#cancel(color(red)(9))3 xx 10/color(red)(cancel(color(black)(3))) = cancel(color(red)(9)) xx y/color(red)(cancel(color(black)(9)))#

#3 xx 10 = y#

#30 = y#

#y = 30#

Answer 2 · 2017-07-30T22:47:30

Use cross-multiplication. #y=30#

Cross-multiply the denominator on each side with the numerator on the other side:
#3 * y=9*10#
#3y=90#
Divide by 3:
#y=30#