Mrs. Thomson spent $240 x 1/3 = $<<240*1/3=80>>80 on food.
She spent $240 x 1/5 = $<<240*1/5=48>>48 on clothes.
So she spent a total of $80 + $48 = $<<80+48=128>>128 on food and clothes.
Hence, she had $240 - $128 = $<<240-128=112>>112 left after buying food and clothes.
Then, Mrs. Thomson saved $112 x 3/4 = $<<112*3/4=84>>84.
#### 84