Question

0.4x+0.3y=1.7 and 0.7x-0.2y=0.8 by substitution method

Answer 1

Hey,
0.4x+0.3y=1.7 .......(i)
0.7x-0.2y=0.8 ......(ii)
Multiplying eqn (i) with 7 and eqn (ii) with 4,
2.8x+2.1y=11.9
2.8x-0.8y=3.2
-........ +...... - (here dot represents gap)
____________
2.9y=8.7
y=3

0.4x + 0.3 y=1.7
0.4x+ 0.3*3=1.7
0.4x+0.9=1.7
0.4x=1.7-0.9
0.4 x=0.8
x=2

#hope it helps....

Answer 2

Equation 1 can also be written as:-
4x/10+3y/10=17/10
Dividing both sides by 10
=> 4x+3y=17
Subtracting 3y from both sides
=>4x=17-3y
Dividing both sides by 4
=>x=(17-3y)/4

Equation 2 can also be written as:-
7x/10-2y/10=8/10
Dividing both sides by 10
7x-2y=8
Substituting the value of x
7*(17-3y)/4 -2y=8
(119-21y-8y)/4=8
Multiplying both sides by 4
119-29y=8*4
119-29y=32
Subtracting 32 from both sides
119-32-29y=0
Adding 29y to both sides
87=29y
Dividing both sides by 29
y=87/29
y=3
Substituting the value of y in equation
7x/10-2y/10=8/10
=>7x/10- (2*3)/10=8/10
Dividing both sides by 10
7x-6=8
Adding 6 to both sides
7x=8+6
7x=14
Dividing both sides by 7
x=2



Hence,x=2 and y=3

Hope this helps!