Name: ______________________________ Period:_________________________
Activity Sheet 3-4
Solving System of Equations with Substitution
Use Substitution of solve each system of equations.
Ex. 2x + 3y = 7
5x – 7y = 3
1st Solve for x in 1st equation:
2x = 7 – 3y
x = 7 – 3y
2
2nd Substitute x value into 2nd equation.
3rd Multiply everything by 2 to get rid of denominator. Solve for y.
4th Substitute y value to get x value.
1. 3x + 2y = 5
5x + 3y = 7
3. –3x + 4y = 14
5x + 2y = 20
2. 4x – 5y = 22
2x – 7y = 20
4. 5x – 2y = 11
4x – 3y = 13
5. Galvanized nails are sold by the pound. Derya bought $2.00 worth of six-penny nails and $3.00 worth
of eight-penny nails for a total weight of 8 lbs. Later she bought $1.00 worth of six-penny nails and $6.00
worth of eight-penny nails for a total weight of 10 lbs. How much per pound does each type of nail cost.
-- What do you know?
-- What are you looking for?
-- Can you write equations that relate what you know to what you don’t know?
-- What concepts are we looking for?
-- After you’ve found our unknown, are the units consistent with what the question asks?
Solve each system of equations by adding or subtracting.
6. 2(x + y) = 7
2(x – y) = 5
8.
3x – 13 = 4y
– 11 = 5y – 3x
10. 3(x – y) = – 9
14 = 3y – 2x
7. 2c + 17 = 5d
8d = 2c + 26
9.
5(a + 3) = b – 6
8 – 5a = 3b + 25
11. 7x + 9y = 32
19 = 2(x + 3) – 9y