If a and b are directly proportional and the value of a becomes 3 times as much, what happens to b

98 ! and brainliest plz ! the below reaction can be categorized as more than one type of reaction. which reactions are these, and what are the types of reactions?

What metric units would you use to measure the thickness of a key

Which of the following is an indication that a substance has undergone a chemical change? a. no new product has been formed. b. the color of the substance has not changed. c. the original constitute has not changed. d. the molecular structure has changed.