—Simon, how old is your father this year?
—______. And we just had a special birthday party for his _____ birthday last Sunday.
A:Fortieth; forty
B:Forty; forty
C:Forty; fortieth
D:Fortieth; fortieth
若a<b,则不等式(a-b)x>a-b,化为“x>a”或“x<a”的形式为( )
____+15=30
____+25=50
____+35=70
____+45=90