Help with number 6? Rlly dont get it.

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

X^2/100+y^2/25=1 the y-intercepts are at: a) (-10,0) and (10,0) b) (0,10) and (0,5) c) (0,-5) and (0,5)

Abari owns 100 shares of stock a and 45 shares of stock b. for the past month, his stocks have been fluctuating inversely. stock a decreased by m cents per share and stock b increased by n cents per share. which equation can be used to find the total change in value of jabari's shares per month?