You can solve simultaneous equations either by substitution, or by elimination by addition, or by elimination by subtraction, or by matrix.

If there are only two equations, like your question here, by substitution is enough.

You substitute x for y, or y for x, so that you end up with only y, or only x, or only one variable/unknown.

3x+4y=18 -----Eq.(1)

4x=2+2y ------Eq.(2)

Say we want only x as the unknown. Then we solve for y in terms of x in Eq.(1). Then we substitute that into Eq.(2). Etc...

3x +4y = 18 ----(1)

4y = 18 -3x

y = (18-3x)/4 -----------(1a)

Substitute that into Eq.(2),

4x = 2 +2*(18-3x)/4

Clear the fraction, multiply both sides by 4,

16x = 8 +2(18-3x)

16x = 8 +36 -6x

Isolate the x-terms,

16x +6x = 8 +36

22x = 44

x = 44/22 = 2 ---***

Substitute that into (1a),

y = (18-3x)/4 -----------(1a)

y = (18-3*2)/4

y = 12/4 = 3 -----***

Therefore, x=2 and y=3. ------answer.

Check those on the original equations:

3x+4y=18 -----Eq.(1)

3*2 +4*3 =? 18

6 +12 =? 18

18 =? 18

Yes, so, OK.

4x=2+2y ------Eq.(2)

4*2 =? 2 +2*3

8 =? 2 +6

8 =? 8

Yes, so, OK.