Question

daca la o cincime dintrun numar a adaug 3 obtin o patrime din a care este numarul a

Answer 1

x : 5 + 3= a : 4 \ inmultim cu cinci 
x + 3 = a : 4 x 5 
 x + 3 = a : 20 \ inmultim cu 20
x + 3 = a
x = a - 3

Answer 2

l------------l------------l-----------l-----------l-----------l (a)
l------------l------------l-----------l-----------l3+3+3+3 (a)

3+3+3+3=12 (un segment)
12x5=60 (a)
12+3+12+3+12+3+12+3=15x4=60 (a)
60=60 (numarul)