# Substituition method

1. Solve the system of equations & find the ordered pairs

x + 9y = 4 (1)

x = 5-9y (2)

2. Solve by the substitution method

4x+9y=60

x=69-9y

3. I am having trouble with two word problems:

a) Train A and B are traveling in the same direction on parallel tracks. Train A is traveling at 40mph and train B is traveling at 48 mph. Train A passes a station at 5:20 p.m. if train B passes the same station at 5:35 p.m. at what time will train B catch up to Train A?

b) The equation y= - 1777x + 27,153 can be used to predict the Number y of gun deaths in the United States x years after 2000 that is x corresponds to 2000, x=2 corresponds to 2002, x = 6 corresponds to 2006, and so on. Predict the number of gun deaths in 2006 and 2008. In what year will the gun death be 9383?

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#### Solution Preview

1. Solve the system of equations & find the ordered pairs

x + 9y = 4 (1)

x = 5-9y (2)

Substitute value of x from (2) into (1)

5 - 9y + 9y = 4

5 = 4

Which is not possible.

Thus there is NO SOLUTION.

2. Solve by the substitution method

4x+9y=60----(1)

x=69-9y------(2)

Substitute value of x from (2) into (1)

4(69-9y) + 9y = 60

276 - 36y + 9y = 60

-27y = 60 - 276

-27y = -216

y = ...

#### Solution Summary

Solves the system of equations & find the ordered pairs.