he saves $860 per month
calculate each of his outgoings
rent =
× $3600 =
= $900
food =
× $3600 =
= $1440
activities =
× $3600 =
= $400
savings = $3600 - ( 900 + 1440 + 400 ) = $860
Set 4 is the correct answer because if you multiply 10 by 10 + 20 times 20, you will get 400 and when you multiply 30 by 30 you also get 400 which is equal to 400 there for you answer would be set 4.
Hope I helped if I did click the thx button ;)
B. j = 32m
Hope this helps!