Show:
Undo
N=
S=
Both
M/D
100

undo +

-

100

3+n=7

N=4

100

6-s=2

s=4

100

f+5=12

F=7

100

4xn=20

N=5

200

Undo -

+

200

16+n=24

N=8

200

15-s=8

s=7

200

F-23=4

f=27

200

nx7=35

N=5

300

Undo X

Divide

300

 N +9=10

n=1

300

s-22=17

S=39

300

56=f+24

F=32

300

n/5=6

N=30

400

Undo divide

X

400

42+n=74

N=32

400

82-S=58

S=24

400

55-f=36

F=19

400

N/7=9

N=63

500

3+5(3+2)=

28

500

N+89=154

N=65

500

103=72-s

S=31

500

F-68=31

F=99

500

25*n=100

N=4