Meredith bought 2/5 kg of shrimps.
courtney bought 1/10 kg of shrimps less than meredith.
(a) find the weight of the shrimps bought by courtney.
(b) find the total weight of the shrimps bought by them.

Step-by-step explanation:

if Meredith bought 20 kg and Courtney bough 10 kg less you'd do 20-10 to find how much Courtney bought, hopefully that makes sense.  We are going to do the same thing here.

That means 2/5 - 1/10.  To subtract fractions you need common denominators, like 5/6 - 1/6 = 4/6.  The bottom numbers need to be the same.  So how do we do that?  Well, that 4/6 can be rewritten as 2/3, they are the same number.  So we want to do the same with either 2/5 or 1/10... or maybe both.  Well 4/6 becomes 2/3 because 4/2 = 2 and 6/2 = 3, so we need to use that thinking.

in 2/5 - 1/10, do you see something we can multiply by to make the bottom numbers the same?  What if you multiplied 2/5 by 3 on the top and bottom?  that would get us 6/15.  Well that's too high, maybe we try 2 then.  4/10.  And hey, that got us a 10, so we idn't have to change 1/10.  Now we can do the problem.

2/5 - 1/10 = 4/10 - 1/10 = 3/10.

So Courtney bought 3/10 kg

To find the total weight we add.  So now we have a similar problem.

2/5 + 3/10  Well we know what to change 2/5 to to get a 10 at the bottom.  

2/5 + 3/10 = 4/10 + 3/10 = 7/10.

So in total they bought 7/10 (seven tenths) of a kilogram.  

Let em know if something didn't make sense.

if you are saying purchasing 3 social media ads and one newspaper ad counts as one purchase then there are:

6 purchases

if you are asking how many of each then:

18 social media ads

6 newspaper ads

$650 per month plus utilities

step-by-step explanation:

just based on the info you gave, it would seem more cost effective to rent at $650 per month plus utilities.   if utilities are, in fact, $150 per month, your monthly living costs would be $800 as opposed to the other option of $825.