For the sake of showing work I will replace the empty space with an x like so...

To find out what x is you must cross multiply (aka butterfly)
***Image of this step is attached below
9*x = 10*90
9x = 900
Next divide 9 to both sides to finish isolating x. Since 9 is being multiplied by x, division (the opposite of multiplication) will cancel 9 out (in this case it will make 9 one) from the left side and bring it over to the right side.
9x ÷ 9 = 900 ÷ 9
1x = 100
x = 100
To make these fractions equivalent the empty spot must be 100

Hope this helped!
~Just a girl in love with Shawn Mendes
Answer:
Sammy needs to pay his mom 5 dollars each time he breaks a rule. His mom will make one exception and only take 2 dollars one time. y represents the total money paid and x is the number of times sammy broke a rule.
Answer:
2, 6, and 7
Step-by-step explanation:
3n is by itself because theres no other numbers that have the letter n.
6m and -11m are like terms bcs they both have the letter m (variable)
-3 and -18 are both like terms bcs they are both just numbers (or constants whatever)
so you would choose options 2, 6, and 7! hope this helps! :)