First you convert the percentage into a decimal. 18% to 0.18, then you multiply that decimal to the price of the item being discounted and bam, you have your price.
Subtract 42 from 44.92 and then divide by 42. So it is 7%
Since triangle ADE is similar to triangle ABC and the scale factor is 2, the following relation must be fulfilled:

The, by substituting the given information, we have

By multiplying both sides by x+2, we get

which gives

Then, by subtracting 4x to both sides, we have

and by adding 8 to both sides, we obtain

then, x is given by

Then, by substitutn