# What are x and y if #7x+5y=18# and #-7x-9y=4#?

##### 2 Answers

#### Explanation:

[1]

[2]

Adding [1] and [2]

[3]

Dividing both sides by

[4]

Substituting

[5]

Simplifying

[6]

[7]

[8]

#x=13/2#

#y =(-11)/2#

#### Explanation:

#7x+5y=18# ----------------(1)

#-7x-9y=4# -----------------(2)

Since the co-efficients of

#7x+5y=18# ----------------(1) ADD with (2)

#-7x-9y=4# -----------------(2)

#-4y=22#

#y =22/(-4)=(-22)/4=(-11)/2#

#y =(-11)/2#

Substitute

#7x +5((-11)/2)=18#

#7x -55/2=18# Multiply both sides by 2

#14x-55=36#

#14x=36+55#

#14x=91#

#x=91/14=13/2#

#x=13/2#