Answer:
X = 4, 1
Step-by-step explanation:
Multiplying out
X^2 - 2x - 3x +6 = 2
X^2 - 5x +4 = 0
Factoring:
X^2 - 4x - X +4
X(x-4) - 1(x-4)
(x-1)(x-4)=0
X= 1, 4
If you have multiple equations with multiple variables, you can either do clever substitutions, or turn it into a matrix on which you can perform linear combinations or multiplications (Gauss elimination)
1 1 1 1
2 1 -1 8
1 -1 1 -5
(note how the above 3 rows represent the 3 equations, just got rid of the variables, plus sign and equals sign)
subtract row1 from row3, that eliminates x and z from row 3.
1 1 1 1
2 1 -1 8
0 -2 0 -6
divide row3 by -2, that will give y a factor of 1
1 1 1 1
2 1 -1 8
0 1 0 3
The last row now says y=3
The answer is nine and one third
Add up minutes
1stmonth+2ndmonth+3rdmonth=320+243+489=1052
how many 200's are there
6 of them (companies want money so they see, ok, you bought like 1 minute, we will charge you for the whole 200 minutes since you got in that zone)
6 times 25=150
cost is $150 (mom is not going to be happy, she spend like 3% of her waking hours takling on the phone)
