In school the ratio of the number of pupils to the number of teachers is 20:1 of the number of pupils is 840 how many teachers are there

Use the elimination method to solve the system of equations -x+5y=-4 and 4x+3y=16

Kayla wants to find the width, ab, of a river. she walks along the edge of the river 65 ft and marks point c. then she walks 25 ft further and marks point d. she turns 90° and walks until her location, point a, and point c are collinear. she marks point e at this location, as shown. (a) can kayla conclude that δ and δ are similar? why or why not? (b) suppose de = 15 ft. what can kayla conclude about the width of the river?

What is the value of x when x + 7 = 21?