It is exactly like multiplying in base ten, just remember where your arithmetic lives

Now the next one is just a bit harder

why is this true?

Remember that multiplication is just repeated addition i.e

i.e we have 1 seven and one left over

And for the last one we have

Now when you multiply just use these compuations and don't forget to carry to the next column.

Also remember what base seven really means is

This is just like base 10 i.e

I hope this helps.