David was thinking of a number. David doubles it, then adds 3 to get an answer of 81.6. What was the original number?

)a smart phone has dimensions of 4.9 inches (height), 2.3 inches (width) and 8.0 millimeters (depth). what is the volume of the smart phone in cubic centimeters? (1 in = 2.54 cm)

What is the slope of a line that is perpendicular to y = 3x + 1

Write the expression in complete factored form. 5n_(c - 3) - n(c - 3) =