Question 442456
They have already solved the 2nd one for x. So let's use that.

Since we know x=y+1, then we can substitute that for where we see x in the 1st.

x+y=4  
(y+1) + y  =4  
2y + 1 = 4
2y = 3
y = 3/2
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Now we need to plug in 3/2 back into one of our original equations.

Let's use the 2nd.

x = (3/2) + 1 
x = 3/2 + 2/2
x = 5/2

So our solution is (5/2, 3/2) or {{{x=5/2}}}{{{y=3/2}}}