Are the following linear, quadratic, or exponential?

What is the square root of 45? (step by step working plz)

Yoku is putting on sunscreen. he uses 2\text{ ml}2 ml to cover 50\text{ cm}^250 cm 2 of his skin. he wants to know how many milliliters of sunscreen (c)(c) he needs to cover 325\text{ cm}^2325 cm 2 of his skin. how many milliliters of sunscreen does yoku need to cover 325 \text{ cm}^2325 cm 2 of his skin?

7. if the value of x varies directly with the value of y, and x = 3 when y = 21. what is the valu y, and x = 3 when y = 21. what is the value of x when y = 105?