Answer:
It would be 18-6 = 12
Step-by-step explanation:

There are two changes of sign, so there are 2 or 0 possible positive roots.

There are two changes of sign, so there are 2 or 0 possible negative roots.
There are 4,2 or 0 possible non-real roots.
The solution rounded to the nearest integer is (-2,6)
The equation looks like this:
26=x*3.5+8.50
where x is the number of pen you bought.
We solve it like this:
first, we subtract 8.50 from both sides:
17.50 =3.5*x
now we divide both sides by 3.5:
5=x
so you purchased 5 pens.
In words it would be: negative one point eight three eight three eight three