4 unknowns needs 4 equations. I'll call the unknown numbers a,b,c,d in that order left to right.
4 + a = b
a + b = c
b + c = d
c + d = 67
let's use substitution to get rid to combine equations and get rid of variables.
If a + b = c then a = c - b
4 + (c - b) = b
4 + c = 2b
If b + c = d then b = d - c
4 + c = 2(d - c)
4 + c = 2d - 2c
4 + 3c = 2d
then we have c + d = 67 so c = 67 - d
4 + 3(67 - d) = 2d
4 + 201 - 3d = 2d
205 = 5d
d = 41
Should be easy now, subtract backwards.
67 - 41 = 26
41 - 26 = 15
26 - 15 = 11
15 - 11 = 4
4, 11, 15, 26, 41, 67