error dont know

what the meaning of the error below:

assign1.c: In function `main':
assign1.c:227: invalid lvalue in assignment

i dont know what to do!

x + y - 10 = z;

^^ that's a bad lvalue. with assignment expressions in the form x = y, x has to resolve to a single variable address. you can't do fancy math on that side.

Post that line (227) and we can help you spot the error (unless you figured it out already).