Răspuns :
( d × 4 + 20 ) : 4 = 12
d × 4 + 20 = 12 × 4
d × 4 + 20 = 48
d × 4 = 48 - 20
d × 4 = 28
d = 28 : 4
d = 7
d × 4 + 20 = 12 × 4
d × 4 + 20 = 48
d × 4 = 48 - 20
d × 4 = 28
d = 28 : 4
d = 7