follow up maths

1. 6 + 2 + 4 = 6+4=10+2=12
2. 8 + 5 + 2 =8+2=10+5=15
3. 8 + 1 + 9 + 2 =9+1=10+8=18
4. 1 + 5 + 5 + 9 =5+5=10+9=19+1=20
5. 4 + 6 + 4 + 9 + 6 =9+4=13+4=17+6=23