Multiple formulas inside a formula

Hiho, i need a quick solution to this if anyone can help me out here, i've been at it for hours...

I figured this part out, as i am using Office 2010, i can have multiple IF's in one formula.. So if anyone can figure out how could i make this formula work.. here's what i need

this is the result
Pc = 13,13 + 17,58 x 1,3 = 35,98 kn/m³

where 13,13 is from G18
17,58 is from G19

how could i make a formula like Pc = (G18) + (G19) x 1,3 = (G18+G19*1,3)...
I can't figure out what i'm doing wrong, where to put the "s, where with the ;s and so on..

PS
sorry if i posted this in the wrong section