Question 232559
Next year Peter will be twice as old as his sister will be. She is three years younger than he. How old is each one now? 
I have this done so far. p+1= 2s and S=p-3
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s = p-3
p+1 = 2(s+1) You had 2 times s, not s+1
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p+1 = 2s+2
Sub for s into the eqn above
p+1 = 2(p-3) + 2
p+1 = 2p-6 + 2
P+1 = 2P-4
P = 5
S = 2