pentru prima:
x/2 - 15 = 3/5
se aduce la acelasi numitor comun = 10
5x -150 = 6 => 5x = 156 => x = 156:5 => x = 31,2
31,2 ..... 3/5
x ...........1 (sau 5/5)
x= 31,2 : 3/5 => x = 31,2 *5 /3 = 52 litri
a doua:
3 * x - 3/4 = 2* x-17
aduci la numitorul comun 4
12x - 3 = 8x - 68
4x = 71
x = 71:4
x=17,75
a treia:
x+y+z=60
z=x+6
5/4*y = y+5
aduci la acelasi numitor comun = 4
5y = 4y + 20 => y =20
inlocuiesti in ecuatie
x+20+x+6=60 => 2x + 6 = 40 => 2x = 34 => x = 17
z = 17 +6
z = 23