Hi everyone. Can anybody explain me how to answear on this question so:

I've got this tree T with vertices of degree 1 and 3 and if T has 10 vertices of degree 3, so how many vertices does it have of degree 1?

Also let say G is connected graph with n vertices and n edges so how can i find how many cycles does G have

How many leaves in a complete 3-ary tree with 10 internal nodes?

I'm sooo confused on this question. Please for any help. Thank you