Answer:
x/90 = 13/130(you can simplify this btw)
x90 x90
X = 9
Make both of them ratios
X to 90 and pick another random one 13 to 130.
Make sure to make them equal to eachother then just solve for x.
You can also compare it to 9 to 90
It would still work:
x/90 = 9/90
x90 x90
X = 9, x would also equal 9
