10-7=3, 7-5=2 so the pattern is -3,-2
Part b the answer is 6 mins because if you use the pattern -3,-2 and add it up minus 3 mins equals 2, and another 3 mins past and it’s -2 and 3 plus 3 is 6
Part C: 3 mins before she came the tank was full because if you switch the subtraction to addition it would be 7+3=10