PLS HELP questions 4, 6, 8. im so lost ah

when you ask multiple questions at once, it feels more like i'm doing your HW for you, not that i'm  helping you understand , i'll answer these but you really should have been able to do these if you really did all the others.  Did you just get tired out?  Why can't you do 4, 6, 8?  what is it that you don't understand?

Step-by-step explanation:

4)   old price = 120   to new price = 240

they ask what is the percent change

How much is the change ( in amount )

the "How much is obvious right?  Old price 120 , new price 240.. change is $120

the percent is   change / old price = 120 / 120  = 1  and to put it in percent , multiply by 100 , so 100 % change

6) old price = 250   amount of change -100

so what percent of 250 is 100  

100 / 250 = 0.4   to get it in percent multiply by 100  = 40%

  old price + change = new price

250 +  ( -100)  =  150   new price is $150

8) 5% mark up  , amount of change = $2.50

so 5% of what = 2.50 ?

X* 5% = 2.5

X* 0.05 = 2.5

X=2.5/0.05

X= $50  was the old price

old price + amount change = new price

50 + 2.50 = 52.50

$52.50 is the new price