Let the number of marbles Stevie has = x.
Given Freddie has twice as many marbles as Stevie
Number of marbles Freddie has = 2x.
Given Danny has 5 more marbles than Freddie .
Number of marbles Danny has = 2x+5.
In total they have 55 marbles
x+2x+2x+5=55
Adding like terms :
5x+5=55
Subtracting 5 both sides
5x=50
Dividing both sides by 5
x=10
Number of marbles Danny has = 2x+5=2(10)+5=20+5=25
