The best thing to do is to look for a college that offers KNEC Bridging courses and resit for your Mathematics exams.
KMTC for instances accepts bridging certificates that have been issued by the Kenya National Examination Council (KNEC). This means that you can bridge subjects you have failed in, to qualify for KMTC courses as long as the examiner is KNEC.
NOTE: KMTC does not offer bridging courses but accepts admission for students who have bridged their subjects.