hi, liz54321! i've been noticing that you have been asking many questions like this in the past 20 or so minutes.

a few people have answered some of those questions, and since all of these are fairly similar, why don't you review those solutions others have given you, and give these problems a try? you got this!

if you have any questions, feel free to ask!

i will show you how to do this problem, and then how about you give one a shot?

first, let's define two variables. i will use a and b for the cow and calf, respectively.

a + b = 990 ("A man bought a cow and a calf for 990 dollars...")

a = 8b ("...paying 8 times as much for the cow as for the calf.")

now let's use substitution to solve.

8b + b = 990

9b = 990

b = 110

to solve for a, let's plug our solution for b back in an original equation.

a + 110 = 990

a = 880

there you go. here is a site that may help you with this, if you are struggling:

https://www.varsitytutors.com/hotmath/hotmath_help/topics/writing-systems-of-linear-equations-from-word-problems

hope this helped! again, feel free to reply to this with any questions you still have on this topic!

(and don't forget to always thank those who have helped you in the past !!)