Question 1015254
<pre>
Girls in that school could have their pick for a bf! :)

S = B + G

If 70% of the students in a school are boys

.70S = B

and the number of girls is 540,

G = 540

{{{system(S=B+G, 0.70S=B, G=540)}}}

1.  Substitute 540 for G in S=B+G.

S = B+540

2. Substitute (B+540) for S in 0.70S=B

0.70(B+540)=B
 
Distribute

0.70B+378=B
      378=B-0.70B
      378=1.00B-0.70B
      378=0.30B
 378/0.30=B 
     1260=B   

There are 1260 boys.

Edwin</pre>