How do you solve this system by elimination?

-5x+7y=11
-5x+3y=19

i don't know how to solve it.

Which function has the smallest y-intercept value

Bismuth-210 is an isotope that radioactively decays by about 13% each day, meaning 13% of the remaining bismuth-210 transforms into another atom (polonium-210 in this case) each day. if you begin with 233 mg of bismuth-210, how much remains after 8 days?

This is about circle theorems. someone asap : (