Step-by-step explanation:
Ok. First of all, we need to follow the order of operations: Parentheses, Exponents, Multiplication, Division, Addition, Subtraction. We don't have any parentheses, exponents, or division to resolve, so you can skip those. So now you have: Multiplication, Addition, and Subtraction. We have multiplication in each term, but each term is fully simplified, so we have Addition and Subtraction left.
With that out of the way, let's go ahead and rearrange this equation so it is easier to solve. (<em>Note: we can only rearrange terms that are positive because subtraction is not commutative. But we can turn negative terms into "positive" terms by the method shown below.</em>)
4a - 7b + 2ab - a + b
4a + (-7b) + 2ab + (-a) + b (<em>Now the terms are all positive, so we can rearrange them, but they still have the same value.</em>)
4a + (-a) + 2ab + (-7b) + b
3a + 2ab + 7b
And there we go. Our answer is fully simplified. If you can understand this, you'll be able to simplify without isolating and rearranging the terms each time.
Hopefully this was helpful and not confusing.
Since two people take both courses, we can subtract two from 7, 8, and 21, giving us 5, 6, and 19.
Add 5 and 6 together to get 11. Since eleven students are in those two groups, we can answer this. The answer will be 11/19.
$7.30 - (3.00+1.75) = $7.30 - $4.75 = $2.55
Divide by 3 (3 = number of erasers)
$2.55/3 = $0.85 per eraser.
X + 2 >= 12
x >= 12 - 2
x >= 10
9x < - 54
x < -54/9
x < -6
so the answer is..
x >= 10 or x < -6