2, 5, 7, 12, 15, 17, 22, -?1) 252) 263) 274) 28
2 + 3 = 5; 5 + 2 = 7; 7 + 5 = 12; 12 + 3 = 15; 15 + 2 = 17; 17 + 5 = 22. Note that 3, 2, 5 are being added in the order to various numbers to get the next number. Therefore 3 should be added to 22 to get the answer.