Girl started with 30 pairs of shoes and donated x pairs.Boy started with 22 pairs of shoes and donated half as many pairs as Girl did.How many pairs of shoes did Girl donate if they had same number of shoes remaining?

Solution:

The two equation given which are in two variables are

1. y = x²-2 x -1 9

2. y + 4 x=5

Writing equation 2 as→y = 5 -4 x

Substituting the value of y in equation 1

⇒ 5 - 4 x = x² - 2 x - 19

⇒x² - 2 x + 4 x -19 -5=0

⇒ x² + 2 x -24=0

⇒x² + 6 x - 4 x - 24=0→→→[Breaking the middle term i.e term containing x]

⇒ x(x+6) -4(x+6)=0

⇒(x-4)(x+6)=0

⇒x-4=0 ∧ x+6=0

⇒x = 4     ∧    x= -6

Put x=4 in equation 2,

y + 4 ×4=5

y + 16=5

y = 5-16

y= -11

As one solution is (-6, 29), The other solution of the system of equation is (4, -11).