If AB = CD, then 3x+4 is equal to 4x-1
3x + 4 = 4x - 1
Add one to both sides to cancel out.
3x + 5 = 4x
Subtract 3x from both sides to cancel out.
5 = x
Now, substitute the 5 in place of the x in the equation for AB (3x+4)
3(5) + 4
15 + 4
19
Final Answer: B) 19