You can bring you data in `A:C` to the format
```
X		
1	20	Y1
2	20	Y1
3	20	Y1
5	25	Y1
10	30	Y1
1	25	Y2
3	42	Y2
6	50	Y2
8	50	Y2
10	50	Y2
```
and then use
```
=QUERY(A:C,"select A, sum(B) where A is not null group by A pivot C")
```
to generate
```
X	Y1	Y2
1	20	25
2	20	
3	20	42
5	25	
6		50
8		50
10	30	50
```
ready to be plotted.