I need help understand how to solve this problem.

Two sides of a triangle mesure 20cm and 30cm. what is the measure of the third side

Maria donates a fixed amount, a, to a charity each month. if she donates $300 in 12 months, what is the equation for a? a. a + 300 = 12 b. a × 300 = 12 c. a × 12 = 300 d. a + 12 = 300 e. a + 32 = 100

You can find the constant of proportionality by finding the ratio of