What is the distance from (-4, -7) to (4, 8) ?

What is the missing step in this proof ?

The ivring berlin learning center would like a possible net profit of $650,000 on its new resource manual it sells to schools. the fixed costs for producing the manual are $780,000 and the variable cost per package is $19.85. if the estimated unit sales are 1,250,000 units, what selling price unit should the ivring berlin learning center try?

Present age of man is 45 years, 5 years back his age was 4 times age of his son what is present age of his son?