Abby said that 22.47 ÷ 2.1 equals 0.107. is abby's answer reasonable

Express the following as a function of a single angle, cos(60) cos(-20) - sin(60) sin(-20)

Ametalworker has a metal alloy that is 30? % copper and another alloy that is 55? % copper. how many kilograms of each alloy should the metalworker combine to create 90 kg of a 50? % copper? alloy?

Aiko jumped rope for 20 min and stopped at 8: 05 when did she start