Question

a+b+c+d=120
a=5/6 din c
c=2b
d= 1/5 din a

Answer 1

le aduci pe toate in functie de 1. 

sa zicem ca le scriem pe toate in functide de c.
deci:
c=2*b=>
=>b=c/2
c=c
a=5/6 *c
d=1/5 *a =1/5 *(5/6*c)=1/6*c
cand le aduni ai :
a+b+c+d =(5/6 *c) + c/2 +c +1/6*c =120 (inmultesti in stanga si in dreapta cu 6, sa 'scapi' de numitor)
5*c+3*c+6*c+c=720 <=>15*c=720 <=>48=c
acum inlocuiest in fiecare si poti afla a,b,d

Answer 2

$a+b+c+d=120 \\ a=5/6*c=\ \textgreater \ c=6a/5 \\ c=2b=\ \textgreater \ b=c/2=\ \textgreater \ b=3a/5 \\ a+ \frac{3a}{5}+ \frac{6a}{5} + \frac{1}{5}*a=3a=120=\ \textgreater \ a=120/3=\ \textgreater \ a=40 \\ b=3a/5=\ \textgreater \ b=(3*40)/5=\ \textgreater \ b=120/5=\ \textgreater \ b=24 \\ c=2*b=\ \textgreater \ c=2*24=\ \textgreater \ c=48 \\ d=1/5*a=\ \textgreater \ d=1/5*40=\ \textgreater \ d=8$