A) 8+5•[20+3•(2+4•6)-15]-3=
= 8 + 5 * [20 + 3 * (2 + 24) - 15] - 3 =
= 8 + 5 * (20 + 3 * 28 - 15) - 3 =
= 8 + 5 * (20 + 84 - 15) - 3 =
= 8 + 5 * 89 - 3 =
= 8 + 445 - 3 =
= 450
B) [150+12•8-(14•2-40÷4)]•10=
= [150 + 96 - (28 - 10)] * 10 =
= (246 - 18) * 10 =
= 228 * 10 =
= 2280
C) 5+5•[5+2•(5+25•1-24÷4)]=
= 5 + 5 * [5 + 2 * (5 + 25 - 6)] =
= 5 + 5 * (5 + 2 * 24) =
= 5 + 5 * (5 + 48) =
= 5 + 5 * 53 =
= 5 + 265 =
= 270