Answer:
It is B
Explanation:
Plug each value possible into the equation
(48+x) / 31 = x/15
If both sides are equal when you plug x in, it's correct
If they aren't equal, it is wrong.
How did I get this equation?
Lets use proportions to solve.
Since they are similar, (the two triangles are similar, meaning that they have the same ratio of the y and x axis values) you can use proportions meaning you make it so x over 15 is equal to the total length by the total bottom length.
If you plug 45 in as x, you get (48 + 45) divided by 31 is equal to 45/15
If you simplify the equation, you get 93 divided by 31 is equal to 3, of which 93 divided by 31 is 3
I think you know that 3=3
so it is correct.