13 × 2 / 5 × 1 / 13 × 5 / 17 and 87 × 85 / 86 should be calculated simply, If I can't understand it, I'll type: 13 times two fifths times 1 / 3 times 17 / 587 times 86 / 85,

13 × 2 / 5 × 1 / 13 × 5 / 17 and 87 × 85 / 86 should be calculated simply, If I can't understand it, I'll type: 13 times two fifths times 1 / 3 times 17 / 587 times 86 / 85,

13×2/5×1/13×5/17
=13*1/13*2/5*5/17
=1*2/17
=2/17
87×85/86
=(86+1)*85/86‘
=86*85/86+85/86
=85+85/86
=85 and 85 / 86