Simplify the expression 3(√144-6)

First work inside the square root symbol 144-6 is
answer 138
Now it says give the square root of that number which falls between 11 and 12

11x11=121
12x12=144

so without using a cal. we can see its about 11. 3 estimated
 when I work it out or use cal. its 11.747
now multipy that numbe by 3

35.24