Question

Please help me I can describe a real-world situation in which opposite quantities combine to make zero.

I can represent addition and subtraction on vertical and horizontal number line diagrams.
I can demonstrate how to add two numbers using absolute value and a number line diagram.
I can interpret sums of rational numbers by describing real-world situations.

Answer 1

I think you will be set for any test.just try to study more! Look in your textbooks and ask your teacher for a study session. 

Answer 2

a hydrogen atom has 0 charge because its two constituents are oppositely charged; and understand p + q as the number located a distance |q| from p, in the positive or negative direction depending on whether q is positive or negative.