determinati x y stiind ca sunt invers proportionale cu 4 si 5 iar x+2y=13

Răspuns :

x=k/4
y=k/5
x+2y=13
k/4+2×k/5=13
5k+8k=260
13k=260
k=260:13=20

x=k/4=20/4=5
y=k/5=20/5=4