During a black friday sale, alberto paid 158.00 for a cell phone that was reduced by 30%. what was the original price of the smart phone? explain how to do this.

The only way to think about this is that the $158 Alberto paid is 70% of the original price.  If you save 30% you pay 70%  (30% + 70% =  100%)

I will put that into math language

$158 = 70% of n   or $158 = .7n  Solve by dividing both sides of the equation by .7
(note that when you divide by a decimal less than 1, the answer will be larger than the starting number - $158 - which is exactly what we want.
To the nearest penny the cost of the phone is $225.71

Many people will try to find 30% of $158 and add it onto $158 but that will not work because the 30% came off the unknown price you are looking for and not the $158. You can't find 30% of a price you don't know. You must talk about it in terms of what you a paying - reread the first thing I wrote at the top of this page.  You can try the wrong way yourself (finding 30% and adding it on)  and when you check it, it won't work.

the law of definite proportions states samples of a compound will always contain the same proportion of elements by mass. in other words, a given compound will always contain the same elements in the same proportions by mass.the law of multiple proportions states when two elements combine with each other to form more than one compound, then the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.

Idon’t have want a lot more