This task is a joint variation task involving only direct proportionality:
Direct variation is one in which two variables are in direct proportionality to each other. This means that as one increases, the other variable also increases and vice - versa.
Joint variation is one in which one variable is dependent on two or more variables and varies directly as each of them.
It allows a scientist to understand the history of metamorphic rock by estimating the temperature, depth, and pressure at which a rock undergoes metamorphism.
Hope that helped!