Question 758258

Please help me to solve this question:

9 + ? x 3/8 = 15
I tried to work out what ? was by logically thinking of the equation as 15 is 3/8's of 9 + ? what ever that figure is. I know that if I convert 3/8 to a decimal it is .375 and 3/8's is almost 4/8's which is a half and so I could calculate that if ? was the number 31
so the equation would look something like this:

9 + 31 x 3/8
40 x 3/8
= 3/8 x 40/1
= 120/8
=15/1
=15

 but the answer they have given on the answer sheet is 16 or 016 but I just am lost on how they got ? to be 16? Could you please tell me how they can get this answer and where abouts I am going wrong in my calculations.
Many thanks for your help

Angie
email address gmbs@xtra.co.nz


You don’t need to make this more complicated than it is. Just solve it as an ordinary fractional algebraic equation


Let ? be Q
Then 9 + ? x 3/8 = 15 can be rewritten as:

{{{9 + Q(3/8) = 15}}}

{{{9 + 3Q/8 = 15}}}


72 + 3Q = 120 ------ Multiplying by LCD, 8
3Q = 120 – 72
3Q = 48
Q, or ? = {{{48/3}}}, or {{{highlight_green(16)}}}


You can do the check!!


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