1) 242 + 537 + 358 + 263 = (242 + 358) + (537 + 263) = 600 + 800 = 1400
2) (374 + 978) + 626 = (374 + 626) + 978 = 1000 + 978 = 1978
3) 7936 + 476 + 15624 = 7936 + (476 + 15624) = 7936 + 16100 = 24036
4) (1685 + 14703) + (5297 + 2315) = (1685 + 2315) + (14703 + 5297) = 4000 + 20000 = 24000