Produsul mezilor = produsul extremilor
a/b = c/d ⇒ a*d = b*c
a) n = (7*27)/9 = 7*3 = 21
b) n = (14*3)/2 = 7*3 = 21
c) n = (48*10)/6 = 8*10 = 80
d) n = (50*8)/80 = 50/10 = 5
e) n = (18*4)/3 = 6*4 = 24
f) n = (7777*13)/1001 = 7777/77 = 101
g) n = (140*9)/90 = 140/10 = 14
h) n = (11*48)/44 = 48/4 = 12
i) n = (37*505)/101= 37*5 = 185
j) n = (5*30)/6 = 5*5 = 25
