Question

х+40=100
100-х=40
х-40=60

Answer 1

×+40=100
×=100-40
×=60

100-×=40
×=100-40
×=60

×-40=60
×=60+40
×=100

Answer 2

х+40=100
х=100-40
х=60

100-х=40
х=100-40
х=60

х-40=60
х=60+40
х=100