a. 150 + 50 : 5 - 2 . 3²
=150 + 50 : 5 - 2 . 9
=150 + 10 - 18
=160 - 18=142
b. 4 .$2^{3}$ - $3^{4}$ : $3^{3}$ + 25² : 5²
= 4 .8 -3 + 5²
=32-3+5²
=29-25
=4
c. 375 + 693 + 625 + 307
=(375+ 625) + (307 + 693)
=1000+1000
=2000
d.17 . 12 . 25 + 51 . 2 . 5 + 85 . 14
=17 . 3.4 . 25 + 17.3 . 2 . 5 + 1190
=17.3.(4.25).17.3.(2.5)+1190
=17.3.100.17.3.10+1190
=51.(100.10)+1190
=51.1000+1190
=51000+1190
=52190