Need help understanding each step, please

A 2-period investment project has the following cash flows at times t=0,1, and 2:20,15, and 46, respectively. Complete the triangle for this project and then answer the following question pertaining to the bottom row of numbers; i.e., the row below the horizontal line. Reading the numbers of the bottom row of the triangle from left to right, what is the value of the second number? QUESTION 11 A 3-period investment project has the following cash flows at times t=0,1,2, and 3:38,42,52, and 54 respectively. Complete the triangle for this project and then answer the following question pertaining to the bottom row of numbers; i.e., the row below the horizontal line. Reading the numbers of the bottom row of the triangle from left to right, what is the value of the third number