5-1=

(a)  

10-9=

(a)  

15-10=

(a)  

4-4=

(a)  

8-7=

(a)  

9-5=

(a)  

9-3=

(a)  

12-7=

(a)  

20-10

(a)  

14-7=

(a)  

2+3=

(a)  

2+2+2=

(a)  

8+8=

(a)  

15+5=

(a)  

9+9=

(a)  

5+5+5=

(a)  

1-1=

(a)  

9-7=

(a)  

4+4+4=

(a)  

6+6=

(a)  

15-15=

(a)  

10-2=

(a)  

2+3+5=

(a)  

1+3+5=

(a)  

9-9=

(a)  

3+3+3=

(a)  

5+6+7=

(a)