let English marks =E
Maths marks = M
Science marks =S
E+M=175 ................(1)
E+S=164...................(2)
E=M+11.......................(3)
PLUGGING VALUE OF "E" IN EQUATION (2) FROM (3)
M+11 +S=164
S=153-M............(4)
PLUGGING VALUE OF "E" IN EQUATION (1) FROM (3)
M+11+M=175
2M=164
M=82
PLUGGING THIS VALUE OF 'M' IN EQUATION (4)
S=153-82
S=71
SCORE OF SCIENCE IS 71