Solve the system using the substitution method.

0.1x + 0.6y = -2.2
0.6x – 0.7y = 4

0.1x + 0.6y = -2.2
0.1x = -2.2 - 0.6y
x = -22 - 6y

0.6x – 0.7y = 4
0.6(-22 - 6y) - 0.7y = 4
-13.2 - 3.6y - 0.7y = 4
-4.3y - 13.2 = 4
-4.3y = 13.2 + 4
-4.3y = 17.2

y = -4

0.6x – 0.7y = 4
0.6x - 0.7(-4) = 4
0.6x + 2.8 = 4
0.6x = 4 - 2.8
0.6x = 1.2
x = 2

Multiply each equation by 10, then
1x + 6y = –22
6x – 7y = 40
The only substitution that would make sense is in the first equation for a 1x:
x = – 6y – 22
Then substitute in equation 2
6(–6y –22) – 7y = 40
–36y – 132 –7y = 40
–43y = 172
y = – 4
then 6x –7(–4) = 40
6x + 28 = 40
6x = 12
x = 2

Standard form: 1/10x+3/5y=-2.2; 3/5x-7/10y=4;
substitute/eliminate x = -6y-22
substitute/eliminate y = -4
Solution: x = 2; y = -4;
or (x, y) = (2, -4)