Question

20x+25y=55,25x+20y=35 then x+y=?​

Answer 1

Answer:

x=-1

y=3

Step-by-step explanation:

20x+25y=55

25x+20y=35

WKT-L.C.M of 20 and 25 is 100

Multiply 20x+25y=55 by 4 and multiply 25x+20y=35 by 5

80x+100y=220

125x+100y=175

Subtracting the equations

-45x=45

x=-1

y=(55-20x)/25= (55-20*(-1))/25=75/25=3

Hope it helps!

Pls mark as brainliest!

Answer 2

$\:\:\:\:\: \huge {\boxed{\bf{\orange{Solution}}}}$

• Divide the equation by 5 , to simply the equations :

$\:\:\: \implies \: \sf 4x\:+\:5y\:=\:11---eq(1)$

$\:\:\: \implies \: \sf 5x\:+\:4y\:=\:7---eq(2)$

• Now , multiply eq(1) by 4 and eq(2) by 5

$\:\:\: \implies \: \sf 4(4x\:+\:5y)\:=\:11)$

$\:\:\: \implies \: {\sf{\red{16x\:+\:20y\:=\:44}}} ---eq(3)$

$\:\:\: \implies \: \sf 5(5x\:+\:4y\:=\:7)$

$\:\:\: \implies \: {\sf{\red{25x\:+\:20y\:=\:35}}}---eq(4)$

• Subtract both the equations now

$\:\:\: \implies \: \sf 25x\:+\:20y\:-\:(16x\:+\:20y)\:=\:35\:-\:44$

$\:\:\: \implies \: \sf 25x\:-\:16x\:+\:20y\:-\:20y\:=\:-\:9$

$\:\:\: \implies \: \sf 9x\:=\:-\:9$

$\:\:\: \implies \: \sf x\:=\: \cancel \dfrac{-9}{9}$

$\:\:\: \bigstar\: \large{\boxed{\bf{\pink{x\:=\:-\:1}}}}$

• Now , substitute the value of x in equation 1 to find out the value of y

$\:\:\: \implies \: \sf 4(-1)\:+\:5y\:=\:11$

$\:\:\: \implies \: \sf 5y\:=\:11\:+\:4$

$\:\:\: \implies \: \sf 5y\:=\:15$

$\:\:\: \implies \: \sf y\:=\: \cancel \dfrac{15}{5}$

$\:\:\: \bigstar\: \large{\boxed{\bf{\pink{y\:=\:3}}}}$

• Now , let us find x + y

$\:\:\: \bigstar \: \sf x\:+\:y$

$\:\:\: \implies \: \sf (-1)\:+\:3$

$\:\:\: \implies \large{\boxed{\sf{\red{2}}}}$

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