x^1/2+y=11 and x+y^1/2=7 find the value of x and y?

Just by inspection, expecting small answers,

Try x=1. y=10 does not work.
Try x=4. y=9. works.

Analytically,

x = (11-y)^2
(11-y)^2 + √y = 7
y = (7-(11-y)^2)^2
y^4 - 44y^3 + 712y^2 - 5017y + 12996
piece of cake, no?
synthetic division by y-9 shows that 9 is a root. The others are nasty (but real numbers)