Question

Mary has 21 coins whose total value is shs 72.There are twice as many five shilling coins as there are ten shillings coins .The rest are one shilling coins .Find the number of ten shillings coins that Mary has (3mks).....PLEASE HELP ME ANSWER THIS.....I HAVE POSTED THIS QUESTION MORE THAN FOUR TIMES.....PLEASSSSSSEEEEE​

Answer 1

Explanation:
Let Mary has
x
number of
10
shilling coins , then
Mary has
2
x
number of
5
shilling coins and
Mary has rest
21
−
(
x
+
2
x
)
=
21
−
3
x
number of
1
shilling
coins. By given condition ,
x
⋅
10
+
2
x
⋅
5
+
(
21
−
3
x
)
⋅
1
=
72

∴
10
x
+
10
x
−
3
x
=
72
−
21
or
17
x
=
51
∴
x
=
51
17
=
3
Hence Mary has
3
number of
10
shilling coins [Ans]