+9479 △ABC ~ △DBE
By looking at the order that the letters are given in the triangle names, we can say that
AC / DE = BC / BE
Since AC = 12 we can substitute 12 in for AC
12 / DE = BC / BE
Since DE = 4 we can substitute 4 in for DE
12 / 4 = BC / BE
Since BE = x we can substitute x in for BE
12 / 4 = BC / x
Since BC = BE + EC we can substitute BE + EC in for BC
12 / 4 = (BE + EC) / x
Since BE = x we can substitute x in for BE, and since EC = 6 we can substitute 6 in for EC
12 / 4 = (x + 6) / x
Now we just have to solve this equation for x. First let's simplify 12 / 4
3 = (x + 6) / x
Multiply both sides of the equation by x
3x = x + 6
Subtract x from both sides of the equation
3x - x = 6
3 apples - 1 apple = 2 apples, so 3x - x = 2x
2x = 6
Divide both sides by 2
x = 3
