Jill wrote the number 40 if her rule is add 7 , what is the fourth number in jill's pattern, how can you check your answer

The first number is 40. The second, third, and fourth number each add 7, so we have 3 steps to get to the fourth step, so we must add 7 *3 = 21 to 40, which is 61.

You just keep adding 7 to the first number.
First number is 40.
Second number is 40+7 which is 47.
Third number is 47+7 which is 54.
Fourth number is 54+7 which is 61.

Or you could do 7 X 3 = 21 and add that to 40.
The answer is 61.