Question

solve que no. 15 & 16

Answer 1

sol. of ques. 15.....

Answer 2

15 )

( x + y)/2 +(3x - 5y)/4 = 2

(2x + 2y + 3x -5y)/4 = 2

(5x - 3y) = 8 --------(1)

x/14 + y/18 = 1
18x + 14y = 18 × 14
9x + 7y = 126 ------(2)

now,
from equation (1)
5x -3y = 8
x = ( 8 + 3y)/5

put x = (8 + 3y)/5 in equation (2)

9( 8 + 3y)/5 + 7y = 126

72 + 27y + 35y = 126 × 5 = 630

62y = 630 - 72 = 558

y = 558/62 = 9

put y = 9 in x = ( 8 +3y)/5

x = ( 8 + 3×9)/5 = 35/5 = 7

x = 7 and y = 9

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16) (4x + 5y)/36 = ( x + y -1)/9

( 4x + 5y)/36 = 4(x + y -1)/36

4x + 5y = 4x + 4y -4

y = -4
put y = -4 in equation (2)
(2x -3y)/3 + 3y = 10
(2x +12)/3 - 12 = 10
(2x +12)/3 = 22
(2x +12) = 66
2x = 54
x = 27

hence, x = 27 and y = -4