If I give my brother $5$ dollars, then we will have the same amount of money. If instead he gives me $10$ dollars, then I'll have twice as much money as he will have. How much money does my brother currently have (in dollars)?
y = your money
b = brother's money
y - 5 = b + 5 <===== given this is y = b + 10
y+10 = 2 ( b-10) <==== given sub in 'y = b+10 '
b+10 + 10 = 2b - 20 Solve for 'b' by adding twent to both sides and subtracting 'b' from both sides
$ 30 = b ( and you have $ 40)
y = your money
b = brother's money
y - 5 = b + 5 <===== given this is y = b + 10
y+10 = 2 ( b-10) <==== given sub in 'y = b+10 '
b+10 + 10 = 2b - 20 Solve for 'b' by adding twent to both sides and subtracting 'b' from both sides
$ 30 = b ( and you have $ 40)