1 persegi panjjang memiliki panjang 3x+10cm dan lebarnya x+10cm jika kelilingnya 72cm hitunglah luas persegi panjang

K = 2 ( p + l )
72 = 2( 3x+10 + x+10 )
72 = 2 ( 4x + 20 )
72 = 8x + 40
72 - 40 = 8x
32 = 8x
x = 32/8
x = 4

p = 3x+10
p = 3(4)+10
p = 12+10
p = 22

l = x+10
l = 4 + 10
l = 14

L = p × l
L = 22 × 14
L = 308 cm²