How do people use algebra in real life situations

What is the y intercept of f(x)=(1/2)^x?

Find the cosine function that is represented in the graph.

Draw a tape diagram to represent each situation.for some of the situations,you need to decide what to represent with a variable andre bakes 9 pans of brownies.he donates 7 pans to the school bake sale and keeps the rest to divide equally among his class of 30 students