Expand the expression and combine like terms. -1/2(-3y+10)

Multiply out the bracket:
(-1/2×-3y)+(-1/2×10)
-1/2×-3= 1.5 as the negatives cancel out
-1/2×10= -5
So the answer is 1.5y-5 or 3/2y-5 if you prefer a fraction