Before calculators were around, why was it's advantageous to use logarithms to calculate roots

Solve the equation 3x2 + 19x + 9 = 0 to the nearest tenth.

Find the solution of this system of equation -7x+y=-20 9x-3y=36

Boris needs to buy plastic spoons. brand a has a box 42 spoons for $2.37. brand b has a box of 72 spoons for $3.57. find the unit price for each brand. then state which brand is the better buy based on the unit price. round your answer to the nearest cent.