3/10y-2/5
we are being asked to factor out the coefficient of the variable.

To factor out the coefficient of the variable, first we must identify it... then we have to determine what it will multiply by to give the second coefficient ...

The coefficient of the variable is 3/10. So let's factor it out...

3/10 (y - ?)

So how do you find the ?... You have to determine 3/10 × what (x) gives you 2/5.
3/10x = 2/5
x = 2/5 × 10/3
x = 20/15 = 4/3

So your factored equation would be

3/10(y - 4/3)