5=3-8y
5=60n^-1 -15
4/8=10n/6
a^-1 x+b+c=d
$\displaystyle 5=\frac{60}{n} -15$
$\displaystyle n \cdot 5=n \cdot \left ( \frac{60}{n} -15 \right )$
$\displaystyle 5n = 60 -15n$
$\displaystyle 5n + 15n = 60 - 15n + 15n$
$\displaystyle 20n = 60$
$\displaystyle \frac{20n}{20} = \frac{60}{20}$
$\displaystyle n = 3$
-Dan
Why don't you give these two a try on your own and post what you have done. They are both very similar to the two examples I already posted an answer for.
The last one LOOKS tricky, but it is very straightforward. a, b, c, and d are just numbers. If it helps, pick some random numbers for them and solve the problem that way first. It will show you the steps you have to take to solve it.
-Dan