To decrease an amount by 8 percent, what single multiplier would you use?

That's far more problems than I usually accept in a single question, but since you're new and obviously a beginner, I'll try to help. 

To Increase an amount by 7% what single multiplier would you use 
We want 7% more than 100% of the amount, so the multiplier is 
(100% + 7%) = 107% = 1.07 
[Remember that "percent" means "per hundred," so we divide a percentage by 100 to get the numerical equivalent.] 

To Decrease an amount by 7% what single multiplier would you use 
We want 7% less than 100% this time, so the multiplier is 
(100% - 7%) = 93% = 0.93 

5 ÷ 0.1 
= 50 

(To One Decimal Place) (0.3 x 2.8)Squared 
[Notation: around here we usually write "squared" as ^2, where the ^ is an exponentiation sign.] 
(0.3 x 2.8)^2 = 0.84^2 = 0.7056 
which is 0.7 when rounded to one decimal place. 

6.38 + 4.52 ÷ 4.71 +9.53 
= 6.38 + (4.52 ÷ 4.71) + 9.53 [assuming operations in the usual order] 
= about 6.38 + 0.96 + 9.53 
= 16.87 

Expand and Simplify 
(x + 2)(x + 3) 
= x^2 + 2x + 3x + 6 
= x^2 + 5x + 6 

Expand and Simplify 
(x + 2)(x - 3) 
= x^2 + 2x - 3x - 6 
= x^2 - x - 6 

x + 1 < 5 
x < 4 [subtracting 1 from both sides] 

Make n the subject of the formula M=3n 
3n = M 
n = M/3