Answer:
The first box (y+4/7=6/7) should have 2/7
---Subtract 4/7 from both sides to get y alone. y=2/7
The second box (17+b=60) should have 43
---Subtract 17 from both sides to get b alone. b=43
The third box (6/7=m+3/7) should have 3/7
---Subtract 3/7 from both sides to get m alone. m=3/7