Help! I’m not quite sure what to do for these, especially 393 and 394

Carson has only $20 bills and $10 bill in her wallet. the total value of the bills is $50. she has 1 more $20 bill than $10 bills. how many each kind of bill does carson have? a. one $20 and two $10 bills b. two $20 bills and one $10 bill c. one $20 bills and three $10 bills d. two $20 bills and two $10 bills

Three times the sum of a number and seven is negative thirty-six. what is the number?

9/10 divide by -3/15 as a mixed number