Answer:
The formula for this is 
The value of x would be 7.14 but since it says round to the nearest tenth it would be 7.1 or 7.10
1. the formula for the slope is

where (a,0) is x1, y1 and (0,2a) is x2, y2. try to see if you can do it now (:
2. take a number x, then step by step do whatever the question asks for example "First, 3 is subtracted from x" so you know the first thing you need to do is x-3, then go on and you'll get an equation which you can use to solve for x, try it!
3. make a set, S, which has multiples of 7. then make a set, T, which has multiples of 13.
now the intersection of S and T is a set having all elements of S, also found in T (basically the numbers that are common to both). try doing it now!
for fourth, this requires a profit formula(that I do not know), must be explained in your book, try going over it, I'm sure you'll find it there!
(x+2/5)7=63/10
then divide both sides by 7
x+2/5=63/70
subtract 2/5 from both sides
and x= 1/2
*x=original number
Answer:

Step-by-step explanation:
