a+b+c+d=345
b=80/100*a; b=4a/5
c= 75/100*4a/5; c=3/4*4a/5; c=3a/5
d= 60/100*3a/5; d=3/5*3a/5; d=9a/25
Facem substitutia:
a+4a/5+3a/5+9a/25=345
25a+20a+15a+9=345*25
69a=8625
a=8625:69
a=125
b=4*125/5; b=100
c=3*125/5; c=75
d= 9*125/25; d=45
a+b+c+d=125+100+75+45=345
