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