2 1/7 : (15a) = 5/14 : (0.8)

0.32 or 8/25

Explanation:

2⅐/15a = ⁵/₁₄/0.8 Multiply both sides by 14

30/15a = 5/0.8 Invert each side

15a/30 = 0.8/5 Multiply each side by 30

15a = 0.8/5 * 30 Divide each side by 15

a = 0.8/5 * 30/15

a = 0.16 * 2

a = 0.32

If you want the answer as a fraction

a = 32/100 = 8/25