You can make this into a fraction, and then simplify it.
15/10, right?
15/10 = 3/2
Then compare 3/2 to the rest of the equation
3/2 = x/16
2 * 8 = 16
so
3 * 8 = x
x = 24
Kim would put x number of pizza slices on her pizza.
So she would be putting on 24 slices on her pizza.