Answer:
1) 20.
2) 30.
3) 47.
4) 86.
5) 27.
Explanation:
The order of operations consist in, first, evaluate the parenthesis, then the exponents, the multiplication, the division, and as last the addition and subtraction. Having this in mind:
1) (28 ÷ 4) + 3 + (10 - 8) × 5
7 + 3 + 2 × 5
7 + 3 + 10
20
2) 12 - 5 + 6 × 3 + 20 ÷ 4
12 - 5 + 18 + 5
30
3) 36 ÷ 9 + 48 - 10 ÷ 2
4 + 48 - 5
47
4) 10 + 8 × 90 ÷ 9 - 4
10 + 80 - 4
86
5) 8 × 3 + 70 ÷ 7 – 7
24 + 10 - 7
27