Question

если 1/5 + 1/7 + 1/11 + 1/13 = a , то чему равно 4/5 + 6/7 +10/11 + 12/13?

Answer 1

4/5=1-1/5. 6/7=1-1/7. 10/11=1-1/11. 12/13=1-1/13.
4/5 + 6/7 +10/11 + 12/13=
1-1/5+1-1/7+1-1/11+1-1/13=
4-(1/5+1/7+1/11+1/13)=4-а.