3,128 = 42(p + 15)
We're trying to find p, which is quite simple.
Simplify.
3,128 = (42 · p) + (42 · 15)
Simplify.
3,128 = 42p + 630
Now, we subtract 630 from both sides.
3,128 - 630 = 42p
Simplify.
2,498 = 42p
Remember...we're simply just trying to isolate p. In order to do that, we must divide both sides by 42.
2,498 ÷ 42 = 42p ÷ 42
Simplify.
≈ 59 = p
** ≈ means "precisely" or "about" **
Therefore, p = 59
However, if your teacher does not want the rounded answer, then here is the full value of p : 59.4761904762
Hope I helped! :)