Question

by using cross multiplication X/6+ y/15 =4 ; X/3 - y/12=19/4​

Answer 1

Answer:

x = -2

x = -2y = 65

Step-by-step explanation:

$\frac{x}{6} + \frac{y}{15} = 4$

$\frac{15x + 6y}{6 \times 15} = 4$

$\frac{15x + 6y}{90} = 4$

$15x + 6y = 4 \times 90 = 360$

15x + 6y = 360 ---------(1)

$\frac{x}{3} - \frac{y}{12} = \frac{19}{4}$

$\frac{12x - 3y}{3 \times 12} = \frac{19}{4}$

$\frac{12x - 3y}{36} = \frac{19}{4}$

$12x - 3y = \frac{19}{4} \times 36$

$12x - 3y = \frac{684}{4} = 171$

12x - 3y = 171 -----------(2)

take equations (1) and (2)

15x + 6y = 360 ---------(1)

12x - 3y = 171 -----------(2)

now multiply (1) with 12 and (2) with 15

$180x + 72y = 4320 - - - (3)$

$180x - 45y = 2565 - - - (4)$

subtract (4) from (3) and find y ...

$27y = 1755$

$y = \frac{1755}{27}$

y = 65

now substitute y in (1) ,

$15x + 6 \times 65 = 360$

$15x + 390 = 360$

$15x = 360 - 390$

$15x = - 30 \\ x = \frac{ - 30}{15}$

x = -2