Please help 11 points worth

The? half-life of a radioactive substance is 20 years. if you start with some amount of this? substance, what fraction will remain in 120 ? years

Arefrigeration system at your company uses temperature sensors fixed to read celsius (°c) values, but the system operators in your control room understand only the fahrenheit scale. you have been asked to make a fahrenheit (°f) label for the high temperature alarm, which is set to ring whenever the system temperature rises above –10°c. what fahrenheit value should you write on the label?

Th perimeter of a rectangular garden is 150 feet. the length is 50 feet longer than the width, w. which equation could be used to calculate the width of the garden? a.) 2w+ 2(w-50) =150 b.) 2w+50 + 2w =150 c.) 2(w+50) + w =150 d.) 2w+ 2(w + 50) = 150 need asap. will give brainliest !