Question

x pe 3= y pe 4 si 3x+4y=75 determinari x si y

Answer 1

x /3=y/4
4x=3y
x=3k
y=4k
3x+4y=75
3*3k+4*4k=75
9k+16k=75
25k=75
k=75:25
k=3
x=3*3
x=9
y=3*4
y=12

Answer 2

x/3=y/4;  4x= 3y
3x+4y=75 /*3
4x-3y=0 /*4

9x+12y=225
16x-12y=0
------------------
25x /=225
x=9

9/3=y/4; 3y=36; y=12