Let:
M = Total money = $20.56
Ca= Cost of the apple = 79 cents = $0.79
Cg = Cost of the granola bar = $1.76
Ms = Total money spent
Mr = Remaining money
So, the total money spent will be:
Ms = Ca + Cg = $0.79 + $1.76 = $2.55
And the remaining money will be:
Mr = M - Ms = $20.56 - $2.55 =$18.01