Games Like MATH IS HORROR

Stuck in a dilapidated asylum, unsure how you got here. You must solve increasingly complex equations to survive. But something sinister follows close behind, waiting for you to slip up and fall within its reach.

Using what knowledge you have of Mathematics, you'll have to solve problems involving: Addition, Multiplication, and Subtraction.
BEWARE: Some puzzles aren't so straight forward, you may have to use the environment.