Explicație pas cu pas:
a=2/3
S =a+b
S=2/3+b
D=2/3-b
S/D=5
(2/3+b)/(2/3-b)=5
(2/3+3b/3)/(2/3-3b/3)=5
[(2+3b)/3] /[(2-3b)/3]=5
(2+3b)/3×3/(2-3b)=5
(2+3b) /(2-3b) =5
2+3b=5(2-3b)
2+3b=10-15b
3b+15b=10-2
18b=8
b=8/18
b=4/9
