1.6x + 1.5y = 1.8
0.4x + 0.3y = 0.6
multiply the bottom equation by -4
1.6x + 1.5y = 1.8
-1.6x - 1.2y = -2.4
add the equations together
0x + 0.3y = -0.6
solve for y
0.3y = -0.6
y = -2
back to the original equations:
1.6x + 1.5y = 1.8
0.4x + 0.3y = 0.6
multiply the bottom equation by -5
1.6x + 1.5y = 1.8
-2x - 1.5y = -3
add the equations together
-0.4x = -1.2
x = 3