757+172:4-712-3•28=

Result: 4

Steps:

• 172 : 4 = 43
• 3 • 28 = 84
• Expression becomes: 757 + 43 - 712 - 84
• 757 + 43 = 800; 800 - 712 = 88; 88 - 84 = 4

So, 757 + 172:4 - 712 - 3•28 = 4.