Can some one give me the answers to this

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

3x + 4y = 5 x- 3y = -7 solve by substitution

The party planning committee has to determine the number of tables needed for an upcoming event. if a square table can fit 8 people and a round table can fit 6 people, the equation 150 = 8x + 6y represents the number of each type of table needed for 150 people.