Iam not understanding these fractions. someone me

What is the missing reason in step 5? linear pair postulategivendefinition of complementary anglescongruent complements theorem

The average human heart beats 1.15 \cdot 10^51.15⋅10 5 1, point, 15, dot, 10, start superscript, 5, end superscript times per day. there are 3.65 \cdot 10^23.65⋅10 2 3, point, 65, dot, 10, start superscript, 2, end superscript days in one year.how many times does the heart beat in one year? write your answer in scientific notation, and round to one decimal place.

Tiffany drives 285,120 feet before lunch and 628,320 feet after lunch. about how many kilometers does she drive all together