36) x/4+2x/5+x/6+77=x
30x+48x+20x+4620=120x
98x+4620=120x
4620=120x-98x
X=4620:22
X=420 lei
37)in cat
timp umplu bazinul ambele robinete deschise concomitent?
(20 + 30) : 2= 50 : 2 = 25 minute
acum aplicam regula de trei simpla
daca in 4 minute ---se umplu------------200 l
in 25 min.........se umplu .......x l
x = (25 x 200) : 4 = 5000 : 4 = 1250 l
Deci bazinul are o capacitate de 1250 l
38) 100%-15% = 85%
1377:85% =1620
100%-10% = 90%
1620:90% = 1800 lei pretul initial
39)
x/4+x/3+12=x-3
x/4+x/3-x=-3-12
3x+4x-12x=-3-12
7x-12x=-15
-5x=-15
x=3
