Hey there!

Maths in WBCS is actually Arithmatics which you may have studied in IX X. There may be a little bit of Algebra, mensuration etc. So don’t worry , work whole heartedly  and do all sums in each chapter which will increase your confidence.

Thereafter go for other books available in the market.For mathematics, Fast track artihmatic by Rajesh Verma of Arihant/ Rakesh Yadav's book on arithmatic for SSC CGL might be useful.

Have a nice day!