Donna bakes biscuits on a rectangular cookie sheet that is 30 centimeters by 50 centimeters. each biscuit had a diameterof 8 centimeters. what is the maximum number of biscuits donna can make on the sheet at once on the cookie sheet.

We know that
[the area rectangular cookie sheet]=30*50> 1500 cm²

let's assume that each biscuit is inscribed in a square of 8 cm side
in the side of 30 cm can be placed > 30/8> 3.75>  3 
in the side of 50 cm can be placed > 50/8> 6.25>  6 

The maximum number of complete biscuits is 3*6> 18 biscuits
the answer is 18 biscuit