6a=30 ⇒ a=5
2c+ 2*5 = 2c+10=20
2c=20-10
2c=10
c=5
4i+5=13
4i=8
i=2
5+ 5x2 = 5+10 = 15.
30 : 3 = 10 → valoarea unei perechi de adidasi
( 20 - 10 ) : 2 = 10 : 2 = 5 → valoarea unui robotel
( 13 - 5 ) : 2 = 8 : 2 = 4 → valoarea a doua cornete cu seminte
( 10 : 2 ) + 5 × ( 4 : 2 ) = 5 + 5 × 2 = 5 + 10 = 15
