Question

. If 10x + 5y = 15 and 5x + 10y = 45 What is the value of x − y ?

A] 6
B] -6
C] 3
D] 36​

Answer 1

Given,

• 10X + 5Y = 15
• 5X + 10Y = 45

To Find,

• The Value Of X - Y.

Solution,

10X + 5Y = 15 •••(Given)

5(2X + Y) = 15

2X + Y = 15/5

2X + Y = 3 •••(1 Equation)

5X + 10Y = 45 •••(Given)

5(X + 2Y) = 45

X + 2Y = 45/5

X + 2Y = 9 •••(2 Equation)

Finding The Value Y in 2 Equation;

X + 2Y = 9 •••(2 Equation)

2Y = 9 - X

Y = (9 - X)/2 •••(3 Equation)

Substituting the Value Of Y in 1 Equation;

2X + Y = 3 •••(1 Equation)

2X + (9 - X)/2 = 3

(4X + 9 - X)/2 = 3

3X + 9 = 3 × 2

3X = 6 - 9

X = -3/3

X = -1

Substituting the Value Of X in 3 Equation;

Y = (9 - X)/2 •••(3 Equation)

Y = (9 + 1)/2

Y = 10/2

Y = 5

Required Answer,

X - Y

-1 - 5

-6