7-4+Application+of+Linear+Systems

=**7-4 Application of Linear Systems.** =  Step 1:  Define Variables. Step 2: Write 2 linear equations. Step 3: Solve using best method - Graphing. Substitution. Elimination.

EX AMPLE(S):

** A store sold 28 pairs of cross-trainer shoes for a total of $2220. Style A sold for $70 per pair and style B sold for $90 per pair. How many of each style were sold? **
Define: a = number of style a sold. b = number of style b sold.

Equations : 70a + 90b = 2220 a + b = 28

Solve : 70a + 90b = 2220 -70(1a + 1b = 28)

-70a - 70b = -1960 70a + 90b = 2220 **The -70a and 70a are going to cancel each other out.** **Add -70b and 90 together, then add -1960 and 2220 together.** 20b = 260 b = 13 Now you know style b sold 13 pairs, figure out how many style a sold.