We have

0.4x + 0.3y = 1.7

0.7x – 0.2y = 0.8

Lets simplify these equations. We can rewrite them as,

⇒ 4x + 3y = 17 …eq.1

⇒ 7x – 2y = 8 …eq.2

To solve these equations, we need to make one of the variables (in both the equations) have same coefficient.

Lets multiply eq.1 by 2 & eq.2 by 3, so that variable y in both the equations have same coefficient.

Recalling equations 1 & 2,

4x + 3y = 17 , on multiplying equation with 2

7x – 2y = 8 , on multiplying equation with 3

We get,

8x + 6y = 34

21x – 6y = 24

On solving the equation, we get,

x = 2

Substitute x = 2 in eq.1/eq.2, as per convenience of solving.

Thus, substituting in eq.2, we get

7(2) – 2y = 8

⇒ 14 – 2y = 8

⇒ 2y = 14 – 8

⇒ 2y = 6

⇒ y = 3

Hence, we have x = 2 and y = 3.