Step-by-step explanation:

1:-1/8+2/5+1/7

lcm of 8,5,7=280

=1(35)+2(56)+1(40)/280

=35+112+40/280

=187/280

2:-3/5+5/6-2/3

lcm of 5,6,3=30

=3(6)+5(5)-2(10)/30

=18+25-20/30

=23/30

Answer:

2+2=4 2+3=5 2+4=62+5=7