Let the greater number be x and the smaller be y.
Then, we have:
2x − 45 = y or 2x − y = 45 .... (i)
2y − 21 = x or −x + 2y = 21 ....(ii)
On multiplying (i) by 2, we get:
4x − 2y = 90 ....(iii)
On adding (ii) and (iii), we get:
3x = (90 + 21) = 111
⇒ x = 37
On substituting x = 37 in (i), we get:
2 × 37 − y = 45
⇒ 74 − y = 45
⇒ y = (74 − 45) = 29
Hence, the greater number is 37 and the smaller number is 29.