Step by step
The question
Question: for which x is f(x) = 10 in this table of f?
f(x) = 10 x = ?
1 Look at the table
The table shows f.
Each x on top has its f(x) right under it.
For example, f of 1 is 4.
x: top row
f(x): right under its x
2 Find where f(x) = 10
This time we know f(x): it is 10.
We look for the x.
f(x) = 10 → 10 in the f(x) row → x = ?
Careful!
Here 10 is f of x.
So we start at 10 on the f(x) row, not on the x row.
Careful: f(x) = 10: find 10 in the f(x) row, not as an x
Find 10 in the f(x) row.
Right above it: x = 3.
So x = 3.
x = 3
3 Check
Let's check: put the x back.
Under x = 3 the table has 10.
So the answer is right!
column: x = 3, f(x) = 10
Let's look back.
First: look at the table.
Then: find where f(x) = 10.
Last: check.
Answer
x = 3