Answer:
x = 12
AB = 39
AC = 24
Explanation:
The sum of AB and BC is equal to the length of AC.
We can write the following equation based on this information :
AB + BC = AB rewrite the equation using given values
4x - 9 + 3x - 12 = 63 add like terms
7x - 21 = 63 add 21 to both sides
7x = 84 divide both sides by 7
x = 12 replace x with 12 in each expression to find the lengths
AB = 4x-9
AB = 4•12 - 9 and
AB = 39
BC = 3x -12
BC = 3•12-12 and
BC = 24