x/a+y/b=1
x=1,y=4:====>1/a+4/b=1.(1)
x=2,y=10:===>2/a+10/b=1.(2)
(1)*2-(2):
-2/b=1===>1/b=-1/2
1/a=1-4/b=1+4*1/2=3
x=4
4*1/a+y*1/b=1
4*3+y*[-1/2]=1
y=22