Idon’t understand how to do this can somebody me

I will have an image attached explaining how to do the distributive property and to continue from there. 

Just as a reminder of distributing the 2x to (x+7), you also have to distribute the - to (3x+1) and since the - has no number after it (like -4) then all you have to do it distribute -1. 

In math you don't normally write a 1. Like 1x is the same as x. 

I hope this helped, comment if you need anymore help.