I'm not too sure myself (cause Im a learning student myself at the age of 16 and I learn it in a completely different language) I cant really understand c) sorry for my poor english but I think I have gave you enough tips to do c)
<h2>Solving Equations</h2>
To solve linear equations, we must perform inverse operations on both sides of the equal sign to <em>cancel values out</em>.
- If something is being added to x, subtract it from both sides.
- If something is being subtracted from x, add it on both sides.
- Same with multiplication and division. If x is being divided, multiply. If x is being multiplied, divide.
We perform inverse operations to<em> combine like terms</em>. This means to get x to one side and everything else on the other.
<h2>Solving the Questions</h2><h3>Question 1</h3>

Because 7 is being added to x, subtract it from both sides:

Because x is being multiplied by 5, divide both sides by 5:

Therefore.
.
<h3>Question 2</h3>

Here, we can group all the x values on the left side of the equation. Subtract 5x from both sides:

To isolate x, subtract 4 from both sides:

Divide both sides by 2:

Therefore,
.
You mean what is the slope of a line parallel to the line whose slope is -2?
The answer is -2... the slopes of parallel lines are equal
Let "x" represent the weight of the toppings. We know that we can have any number of toppings. This means that one may ask for no toppings at all too.
Now, we have been told that "S" is the weight of the special sundae in kilograms. This definitely included the "mandatory" 2 kilograms of ice cream. Therefore, S will be at-least equal to 2.
Thus, the inequality that describes S, the weight of the special sundae in kilograms at Ping's Ice Cream Palace is given as:
kilograms.
It can be seen that as x increases, S increases too and if an order does not want any toppings in it then the weight of the special sundae will be a minimum of 2 kg which is the weight of the ice cream.