Answer:
117 sweets
Explanation:
Please see attached picture for full solution. (model method)
S, N and R represents the number of sweets Sarah, Natasha and Richard have respectively.
Alternatively,
Let the number of sweets Sarah have be 4x.
Number of sweets Natasha have= 2x
Number of sweets Richard have= 3x
Sarah gets 13 more sweets than Richard
4x= 3x +13
4x -3x= 13
x= 13
Total number of sweets
= 4x +2x +3x
= 9x (simplify)
= 9(13) (subst. x=13)
= 117 sweets