Question

0.4x +0.3y = 1.7
0.7x -0.2y = 0.8​

Answer 1

Step-by-step explanation:

4x +3y = 17

7x -2y = 8

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28x+21y=119

28x+8y=32

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0+13y=87

y=87/13

Answer 2

Answer

$\sf \dashrightarrow 0.4x + 0.3y = 1.7 \: \: --- (i)$

$\sf \dashrightarrow 0.7x - 0.2y = 0.8 \: \: --- (ii)$

1st we have to multiple whole equation with 10 for easier calculation.

$\sf \dashrightarrow 4x + 3y = 17$

$\sf \dashrightarrow 7x - 2y = 8$

By first equation,

$\sf \dashrightarrow 4x + 3y = 17$

$\sf \dashrightarrow 4x = 17 - 3y$

$\sf \dashrightarrow x = \dfrac{17 - 3y}{4}$

Now, let's find the value of y by second equation.

$\sf \dashrightarrow 7x - 2y = 8$

$\sf \dashrightarrow 7 \bigg( \dfrac{17 - 3y}{4} \bigg) - 2y = 8$

$\sf \dashrightarrow \dfrac{119 - 21y}{4} - 2y = 8$

$\sf \dashrightarrow \dfrac{119 - 21y - 8y}{4} = 8$

$\sf \dashrightarrow \dfrac{119 - 29y}{4} = 8$

$\sf \dashrightarrow 119 - 29y = 8 \times 4$

$\sf \dashrightarrow 119 - 29y = 32$

$\sf \dashrightarrow -29y = 32 - 119$

$\sf \dashrightarrow -29y = -87$

$\sf \dashrightarrow y = \dfrac{-87}{-29}$

$\sf \dashrightarrow\boxed{\sf y = 3}$

Now, we can find the value of x by first equation.

$\sf \dashrightarrow 4x + 3y = 17$

$\sf \dashrightarrow 4x + 3(3) = 17$

$\sf \dashrightarrow 4x + 9 = 17$

$\sf \dashrightarrow 4x = 17 - 9$

$\sf \dashrightarrow 4x = 8$

$\sf \dashrightarrow x = \dfrac{8}{4}$

$\sf \dashrightarrow \boxed{\sf x = 2}$

Hence, the values of x and y are 2 and 3 respectively.