It has become somewhat fashionable to have students derive the Quadratic Formula themselves; this is done by completing the square for the generic quadratic equation ax2 + bx + c = 0. While I can understand the impulse (showing students how the Formula was invented, and thereby providing a concrete example of the usefulness of abstract symbolic manipulation), the computations involved are often a bit beyond the average student at this point.
(n+20)*2 = 99.2
distribute
2n + 40 = 99.2
subtract 40 from each side
2n = 59.2
divide each side by 2
n = 29.6
The first step to solving this is converting these mixed numbers into improper fractions. You would do that by multiplying the denominator by the whole number and adding the numerator to that number; this number replaces the numerator. It would look something like this:
1 8/10 --> 18/10
2 2/5 --> 12/5
Now, to subtract the second fraction from the first one, the denominators of both fractions must be the same. We can make them the same by multiplying the second fraction by 2:
12/5 * 2/2 = 24/10
Now we can set up the equation as:
18/10 - 24/10 = -6/10 --> -3/5
The answer is negative 3/5.
I hope this helps.
Inequality : 2n + 2 > 16
2n > 16 - 2
2n > 14
n > 14/2
n > 7
-> Answer C
