Step by step in numerical form
X+y=5.90
2x + 4y = 16.80
This is set up for elimination from what I believe.
4(X + Y = 5.90)
2x + 4y = 16.80
4x + 4y = 23.60
2x + 4y = 16.80
6x = 40.40
X = 6.73
Now for Y, plug in the x value for any equation.
2(6.73) + 4y = 16.80
13.46 + 4y = 16.80
4y = 3.34
Y = 0.835 OR 0.84 rounded up.
Hope this helped!
X = 6.73 Y = 0.84