Answer:
0.5
Step-by-step explanation:
If you add 0.5 to -0.5, it will equal 0.
The sum of two numbers and their difference is 30.
Answer:
The correct answer is 18
the correct expression is 
Step-by-step explanation:
let the number be n
therefore if he is required to multiply n by 4 and added to 6 we have

given that he did otherwise by adding 6 to n and multiply by 4 we have

Firstly we need to solve for n in equation 2

Dividing both sides by 4 we have

In order to solve for the correct answer let us input n=3 in equation 1 we have

To solve this problem you must apply the proccedure shown below:
1. You have that:
- He sales 13 gold rings and 18 silver rings in 9405 euros.
<span> - The cost of the silver ring is three times the cost of the gold ring.
2. Keeping the information above on mind, you have the following system of equations:
x: the gold ring.
y: the silver ring.
x+y=</span>9405
<span> x=3y
3. Then, you have:
(3y)+y=9405
y=9405/4
y=2351.23 euros
x=3y
x=3(</span>2351.23)
<span> x=7053.75 euros
The answer is:
- Gold ring=</span>7053.75 euros
- Silver ring=2351.23 euros<span>
</span>