Can someone help me with these?

When i add money am i supposed to make it like this 7+12 or 7.00+12.00 because i got 19 dollars for my answer

What is the best way to answer questions with a x expression in the question. for example 3x + 10x=?

Evaluate 5 + 6 · 2 – 8 ÷ 4 + 7 using the correct order of operations. a. 22 b. 11 c. 27 d. 5