Ibought 8 shirts that cost an average of $27. my sister then added 3 shirts. the 11 shirts had a mean cost of 28.50. how much did my sister’s shirts cost? need by tomarrow can u also put how u got it so i get it

If m 17 27 90 63 ** picture is attached

Math it's appreciated. (picture provided)

Asmall business produces and sells balls. the fixed costs are $20 and each ball costs $4.32 to produce. each ball sells for $8.32. write the equations for the total cost, c, and the revenue, r, then use the graphing method to determine how many balls must be sold to break even.