Suppose you bought a pizza for $8.00. you also bought a salad but you can not remember how much you paid and you can not find the receipt. you know the total amount you spent was $10.00. which equation would best to answer to find the cost to the salad
a: 8.00+$=10.00
b: 8.00+10.00=$
c: 8.00 x $=10.00
d.10.00 x $ = 8.00

The best equation would be A.

with A you get to calculate what is the value of $. 

8 + $ = 10 (10 is the total value of your receipt and 8 is the price of pizza)
$ = 10 - 8 (we transfer the price of pizza on the other side to the total amount of your receipt and calculate the remaining amount)
$ = 2

We see that the remaining amount is 2$, which means the salad cost s2$ :)