Question

0.3x-0.2y=4
0.4x+0.3y= 73/19

Answer 1

{3/10 x - 2/10 y = 4, 4/10 x + 3/10 y = 73/19}\[\left\{x\to \frac{220}{19},y\to -\frac{50}{19}\right\} \]

Answer 2

x = 11.57

y = -2.63

Answer 3

0.3x-0.2y=4(*3) 0.9x-0.6y=12 1.7x=146/19+12
0.4x+0.3y= 73/19(*2) 0.8x+0.6y= 146/19(add both sides) 1.7x=374/19

x=11.5
.3*11.5-0.2y=4

Answer 4

The following Mathematica expression replaces the x and y solutions into both equations. If the LHS is equal to the RHS, then Mathematica returns "True". Some of the original fractions have been simplified.\[\left\{\frac{3 x}{10}-\frac{y}{5}=4,\frac{2 x}{5}+\frac{3 y}{10}=\frac{73}{19}\right\}\text{/.}\left\{x\to \frac{220}{19},y\to -\frac{50}{19}\right\} \to \{\text{True},\text{True}\} \]The original coefficients were rationalized. Why would one do that? Well the answers are exact.