2a+10b-c + -3a +5b + c = -a +15b
Subtract the equations straight down. So we'll subtract the x terms together
5x - 5x = 0x = 0
meaning the x terms effectively go away after subtraction
Then we do the y terms together in the same exact order
y-3y = -2y
Then finally the right hand side values
6 - (-5) = 6+5 = 11
All of that work done indicates we have 0x-2y = 11 which is the same as -2y = 11. Divide both sides by -2 and we end up with y = -11/2
This answer isn't listed so I'm thinking there's a typo your teacher made somewhere.
Answer:
a)7x-3x
b)4+28y
Step-by-step explanation:
first one follow bidmas
2nd one just do 4 times 1 =4 and 7y times 4 equals 28y
The probability that the arrow will land on any of them <em>once</em> is 1/4.
The probability that the arrow will land on any of them <em>twice</em> is 1/4 * 1/4. This is because the probability of Event A <em>and</em> Event B is P(B) * P(A).
Based on this:

1/256
Hope this helps, let me know if I missed anything!