Question

alright, i want an explanation on how to do these so i can do the rest on my own...

the first problem is
j/3 = 2/5

how do i solve that?

Answer 1

Multiply both sides of the equation by 3. You want to get an equation with just j on one side.

Answer 2

One way is to cross multiply.
5j = 6
j = 6/5

Another way is to multiply both sides by a number that will clear both the 3 and the 5 from the denominator. Such a number is 15. Like this.
15*j/3 = 15*2/5
5j = 6
j=6/5
I hope this helps.

Answer 3

You times j by the reciporacal:

3/1 x j/3

Then whatever you do to oneside you have to do to the other:

j=2/5 x 3/1

Find a common denominator:

2/5 x 15/5 = 30/5

Which reduces to 6/1 or just 6

So j=6

Answer 4

multiply both sides by 3/1 and simplify