notam cu X pomii in total
Prima zi:
meri = 3/8×X
A 2-a zi:
peri = 5/7×(X-3/8×X)
A 3-a zi:
pruni = X-20
Total:
3X/8+5/7×(X-3X/8)+20 = X
3X/8 + 5/7 ×(8X-3X)/8 + X-20 = X |×56
7×3X + 5×8 ×5X + X-20×56 = 56X
21X + 40 × 5X+56X - 1 120 = 46X
82X - 46X = 1 120-40
36X = 1 080
X = 1 080:36
X = 30 (pomi)