You find one half of a cake in the fridge. You give two-fifths of what remains, how much of cake is left? And please elaborate

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?

Anyone know these questions? i need ,.

When solving a logarithm equation, how do you find the missing variable ?