Your question asks how to multiply equations....but the numbers you provide are an addition....
1/8 + 7/4 to ADD them , you need a common denominator
1/8 + 14/ 8 = 15/8 = 1 7/9
IF you want MULTIPLY them:
1/8 X 7/4 just multiply the numerators (top numbers) and multiply the bottom numbers
= 7/32