Siti had 135 buttons. 5/9 of the buttons were red and the rest were blue. She used 64 red buttons and bought some more blue buttons. She had 84 buttons left in the end. How many blue buttons did Siti buy?

Siti bought 13 blue buttons

Step-by-step explanation:

for not to get confused, we are going to solve the problem step by step

Siti had 135 buttons

5/9 of the buttons were red and the rest were blue

let's calculate how many buttons were red out of 135

135 * 5/9 = 75

if 75 buttons were red and the rest were blue, we can calculate how many were blue

135 - 75 = 60

says she only use 64 red buttons

if we had 75 red buttons and she used 64

75 - 64 = 11

she tells us that she had 84 buttons left, from which we know she had 11 red buttons that had been left over and 60 blue ones that she did not use, so we can calculate how many blue buttons she bought since we have the total number of buttons that she has now

84 - 60 - 11 = 13

Siti bought 13 blue buttons