i’ll mark brainiest!! how do u get the rate of change for #2? and what’s the greatest rate of change out of all of them?

If a 36 inch yardstick casts a 21 foot shadow, how tall is a building whose shadow is 168 feet? what is the scale factor

Why can't my rank go i have 1723 points, but my rank is only at ambitious, which is only 250 points! like, (p.s. i know this isn't related to math, but i just don't know why it's doing this and i would really appreciate if someone could tell me whats going on with this)

Carli has 90 apps on her phone. braylen has half the amount of apps as theiss. if carli has three timesthe amount of apps as theiss,how many apps does braylen have? let b represent the number of braylen's apps and t represent the number of theiss's apps.