Pls problemele 3 si 4!! Repede va rog frumossss!!

4.) Notam x- fete, baieti - 2/3x
x+2/3x=800
5/3x=800
x=800 : 5/3
x=480
2/3 x= 2/3 · 480=320

3.
    2 elevi in banca...........2 banci libere
    3 elevi in banca..........6 banci libere
    (3 * 2 + 6) * 2 = 24 elevi
    3 * 2 + 6 + 2 = 14 banci
4. f + b = 800
    b = 2/3 * f
    f + 2f/3 = 800
    3f + 2f = 2400
    5f = 2400
    f = 2400 : 5
    f = 480 fete
    b = 480 * 2/3 = 320 baieti