Tính ‐ 3/7 - (2/3 - 3/7) ; 2/15 : (1/3 × 4/5 - 1/3 × 6/5)

Bài 1: a,‐3/7-(2/3-3/7)
           b,2/15:(1/3×4/5-1/3×6/5)
bài2:tìm x biết 
a,3/4+1/4×x=5/8
b,25%×x=‐1,25