Answer:
x=50.7
Step-by-step explanation
90+38+x+1.3=180
90+38
Add these numbers
=128
128+x+1.3=180
128+x+1.3
Add these numbers
128+1.3=129.3
129.3+x
129.3+x=180
129.3+x
sort elements
x+129.3=180
129.3
convert this to a fraction
1293/10
x+1293/10=180
x+1293/10=180
Move each term from the right to the left side and change a sign of every element
x+1293/10-180=0
x+1293/10-180
subtract these number
1293/10-180=1293/10-1800/10
=-507/10
x-507/10=0
f (x)=x-507/10
a=1
b=-507/10
x-507/10=0
move each number from the left a the right side and change a sign of every element
x=507/10
therefore x=50.7