Adam has 5 blue pencils. How many red pencils would he need to have so that the ratio of blue pencils to red pencils is 1:2? PLZ HELP

Which of those sequences is a geometric sequence

How do i start to solve? would appreciate a walk-thru! a bird sitting 16ft above the ground in an apple tree dislodges an apple. after how many seconds does the apple land on the ground? (assuming that no branches will interfere with it's fall)

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