Tatuya, Ivanna, and Dorothy took a quiz together. Tatuya scored twice as much as Ivanna, and Ivanna scored 3/5 times as many marks as Dorothy. If Dorothy scored 90 marks, calculate the average marks scored by the three.
Since Dorothy scored 90 marks, and Ivanna scored 3/5 times as many marks, Ivanna scored 3/5*90 = 
<gadget id="calculator">90*3/5</gadget>
<output>54</output>
54 marks.
Together, Dorothy and Ivanna scored a total of 54+90 = 
<gadget id="calculator">54+90</gadget>
<output>144</output>
144 marks.
If Tayuta scored twice as many marks as Ivanna, she scored 2*54 = 
<gadget id="calculator">2*54</gadget>
<output>108</output>
108 marks.
The total marks the three scored altogether is 108+144 = 
<gadget id="calculator">108+144</gadget>
<output>252</output>
252 marks.
The average marks for the three are 252/3 = 
<gadget id="calculator">252/3</gadget>
<output>84</output>
84 marks.

<result>84</result>