`(1/5)x + (1/2)y = 8, x + y = 20` Solve the system by the method of substitution.

Express `y` from the second equation: `y = 20 - x.` Then substitute it into the first equation:

`(1/5)x + (1/2)(20-x) = 8,` or

`(1/5)x - (1/2)x + 10 =8,` or

`-(3/10)x=-2,` or

`x=2*10/3=20/3 = 6 2/3.`

Therefore `y = 20 - x = 13 1/3.`

The answer: x=6 and 2/3, y=13 and 1/3.