In general, if we have 
then 
Thus, the first answer choice is correct.
Answer:
120 Books
Step-by-step explanation:
60% of 120 is 72
When you add the equations in (a) you get 7x+y=24.
When you subtract the equations in (b) you also get 7x+y=24.
That means to solve both systems you can work with the same equation. However that is not enough. We must have two equivalent equations. We found only one.
Notice however that in the (b) we can take the first equation and divide every term by 2. When we do this we get 4x-5y=13. That’s the first equation in (a).
So both systems can be solved by working with the same two equations. These are 5x-5y=13 and 7x+y=24. And since we have two equations and two unknowns (the number of equations matches the number of variables) there is only one solution — one x and y that would make both systems true — solve both systems.
Basically we showed the systems are equivalent!
Answer:
3 and 1/2
Step-by-step explanation:
Answer:
110 pounds
Step-by-step explanation:
I'm sorry if I am using algebra:
Take Ellen as x as we don't know their weight.
John is 1.5 times as much as Ellen so:
1.5x= 165 pounds
x= 165 divided by 1.5
x= 110 pounds
Ellen weighs 110 pounds
