A student scored an average of 80 marks in 3 subjects: Physics, Chemistry and Mathematics. If the average marks in Physics and Mathematics is 90 and that in Physics and Chemistry is 70, what are the marks in Physics? Select:
A) 54
B) 76
C) 87
D) 80
E) 82
Given M + P + C = 80 * 3= 
<gadget id="calculator">80 * 3</gadget>
<output>240</output>
240 --- (1)   M + P= 90 * 2= 
<gadget id="calculator">90 * 2</gadget>
<output>180</output>
180 --- (2)   P + C= 70 * 2= 
<gadget id="calculator">70 * 2</gadget>
<output>140</output>
140 --- (3)   Where M, P and C are marks obtained by the student in Mathematics, Physics and Chemistry.   P= (2) + (3) - (1) = 180 + 140 - 240= 
<gadget id="calculator">180 + 140 - 240</gadget>
<output>80</output>
80   Answer: 80
<result>D</result>
A student scored an average of 80 marks in 3 subjects: Physics, Chemistry and Mathematics. If the average marks in Physics and Mathematics is 90 and that in Physics and Chemistry is 70, what are the marks in Physics?