Sumif horizontally (same row)

I need to sum a row, summing values that have a certain value in the preceding cell.

For example:

A B C D E F G H SUM

x 7 y 8 x 4 z 4 11 based on a formula like =sumif((a1,c1,e1,g1),"x",(b1,d1,f1,h1))

Or if there were a criteria such as =Sumif(a1:h1,"precedingcell=x",a1:h1)

No luck yet finding a formula that will work.

Thanks for the help.

Perfect! Thanks!!