Pls help me solve this i will give lots of points

Translate the word phrase into a math expression. 15 fewer than the product of 4 and a number. (pls immediately)

What is true about the dilation? it is a reduction with a scale factor between 0 and 1. it is a reduction with a scale factor greater than 1. it is an enlargement with a scale factor between 0 and 1. it is an enlargement with a scale factor greater than 1.

Ariana starts with 100 milligrams of a radioactive substance. the amount of the substance decreases by 20% each week for a number of weeks, w. the expression 100(1−0.2)w finds the amount of radioactive substance remaining after w weeks. which statement about this expression is true? a) it is the difference between the initial amount and the percent decrease. b) it is the difference between the initial amount and the decay factor after w weeks. c) it is the initial amount raised to the decay factor after w weeks. d) it is the product of the initial amount and the decay factor after w weeks.