Calculate the total surface area of the triangular pyramid.

45

Step-by-step explanation:

15+10= 25 + 20 = 45

they sell 240 sw =)))

Step-by-step explanation:

x= the number of b water they sold

y= the number of sw they sold

because they sold a total of 390 items => x+y= 390   (1)

because they sold water for $2 a bottle and the sandwiches for $4 each => 2x + 4y= 1260   (2)

(1) and (2) => x=150 ; y=240.

i hope this will help you =)))