# Tutor profile: Hannah S.

## Questions

### Subject: Chemistry

What is the pH scale and how is it used?

The pH scale measures acidity or alkalinity of a substance by accounting for hydrogen and hydroxl ions. If the pH is high, it means the substance has more hydroxl ions and it is more basic. On the other hand, if the pH is high according to the scale, there are more hydrogen ions and the substance is more acidic. Acids are measured by a 1-6 (less than 7) on the pH scale, 7 is neutral, and 8-14 (greater than 7) is basic

### Subject: Biochemistry

What makes up DNA and what structure is it?

The structure of DNA is known to be a double helix through findings of Watson and Crick. DNA was also found to be made up of nucleotides, which in turn are made up of a phosphate group, a sugar group, and a nitrogen base of which there are 4 types.

### Subject: Algebra

solve the system: x+y=20 , x=4y+10

First, the question is asking you to combine the two given equations to solve for an answer. Since it does not specify, we must find both x AND y. To start, since you are given what x is equal to, you plug in "4y+10" (what x is equal to) for x in the other equation given. Therefore, you now have 4y+10+y=20. Combine the y by adding them together so it is 5y+10=20 and now solve for y. First subtract 10 from both sides so the equation remains balanced, and then divide by 5 to get the y by itself. So it would go from 5y+10=20 to 5y=10 to y=2. Then, to find x you plug the y we found back into one of the given equations. I think the second one would be easiest. So you have x=4(2)+10 and use order of operations to find the answer. Multiply first, then add. Therefore, x would equal 18.

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