Question

If df=78, de=5x-9, and ef=2x+10, find ef

Answer 1

As e is point between df. So we can write df as 
df = de + ef

As given df = 78 , de = 5x - 9 , ef = 2x + 10.

So we can write

78 = 5x - 9 + 2x + 10

78 = 7x + 1

On subtracting 1 on booth side

78 - 1 = 7x +1 - 1

77 = 7x

On dividing both side by 7.

$\frac{77}{7} = \frac{7x}{7}$

11 = x

So x = 11.

So ef = 2x + 10 = 2*11 + 10 = 22 + 10 = 32