There are 18 girls in the class and 6 boys.
#5 is very nicely and correctly done.
#7 says: "No matter what X may be, this function of it is always 9 more than 1/2 of X .".
That's a very powerful statement. Now you know that if X is ever 2, the function will be 1/2(2)+9 which is 10.
If X is ever zero, the function will be 1/2(0)+9 which is 9. If X is ever a cow, the function will be 1/2 of a cow, plus the number 9. Which makes no sense, but that's what the function says.
So, when X is -8, the function is 1/2 of -8, plus 9. Which is 5 ... the 'f' of -8.
Whatever X happens to be at the moment, just write that number in place of X in the function, and it'll show you the function of what X is.
f(a bazillion) = 1/2(a bazillion) + 9 .
f(a-28) = 1/2(a-28) + 9 (but simplify it)
X is 66 degrees, you just subtract 24 to 90 and it gives you 66.
Linear equations are all solved the same way. Figure out the operations performed on the variable. Undo those in reverse order.
Here, the variable is
- divided by 2
- has -7 added.
In reverse order, we undo these operations by
- adding 7
- multiplying by 2.
Whatever we do to one side of an equation, we must also do to the other side. That is how the equal sign remains valid.
2 = m/2 -7
2 +7 = m/2 -7 +7 . . . . . add 7
9 = m/2 . . . . . . . . . . . . simplify
2*9 = 2*m/2 . . . . . . . . multiply by 2
18 = m . . . . . . . . . . . . . simplify. (You know that 2/2 = 1, and m*1 = m.)
The answer is m = 18.
_____
Check:
.. 2 = 18/2 -7
.. 2 = 9 -7 . . . . . . . true. The answer checks OK.
When I do this the 0.38 per one bagel is rounded
