f.1 maths

可唔可以教我尼4題如可以..我會選你為最佳回答....
Q5)Find the values of a and b such that in the expansion of (x+a)(x+b) , the coefficient of the x term is a postive number and the constant term is a negative number.

Q6)150 balls are put into two boxes A and B . If the number of balls in box B is a multiple of that in boxA , suggest two pairs of the numbers of balls in boxes A and B.

Q7)Jenny wants to send a parcel to her uncle. the postage is $3802. She has some $1.4-stamps , $2.5-stamps and $3-stamps. Suggest two ways of paying the postage using these kinds of stamps.
Q8)Suggest two strategies to estimate the value of the expression 103+152+143+128+175