a: \(=\left(5^2+3\right):7=4\)
b: \(=7^2-3^2+8\cdot25=40+200=240\)
a) (519 : 517 + 3) : 7
= (52 + 3) : 7
= (25 + 3) : 7
= 28 : 7
= 4
b) 79 : 77 - 32 + 23 . 52
= 72 - 9 + 8 . 25
= 49 - 9 + 200
= 40 + 200
= 240
c) 1200 : 2 + 62 . 21 + 18
= 600 + 36 . 2 + 18
= 600 + 72 + 18
= 672 + 18
- 690