Convert the decimal expansion 0. to a fraction

Will give brainliest sum of arithmetic series (sigma notation) find the numerical answer to the summation given below. (image shown below)

What is the length of the missing leg in this right triangle? 18 mm 24 mm 26 mm 32 mm

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'