How do you do #18 in Test 6 Section 3 without a calculator?

Practice Test 6, number 17, no calc.

Test 3 Section 3 #20

Test 3 Section 3 #19

Test 3 Section 3 #18

Test 3 Section 3 #17 (grid-in) please

Test 1 Section 3 number 19. Thanks!

Test 1 Section 3 number 18. Thanks